JPS62134603A - Photoelectric switch - Google Patents

Abstract

PURPOSE:To detect objects from a close distance up to a long distance by using a Fresnel lens consisting of plural partial lenses, which are different in eccentricity and radius of curvature from one another in accordance with positions of lens faces, as the lens in light projecting and receiving part to extend the range of reception of irradiated light. CONSTITUTION:The same Fresnel lenses 12 and 13 are provided on the front of a light projecting part 10 and a light receiving part 11 of a photoelectric switch. The lens consists of partial lenses 12a-12f different in radius of curvature and eccentricity from one another, and partial lenses are so set that different areas are irradiated successively without overlapping when a LED 1 is arranged in the focus position. With respect to the lens 13 constituting the light receiving part 11, a photodetector 2 is arranged in the focus position. In this constitution, the crossing area between light projection and light reception is the detection area, and the area from a close distance to a long distance of the photoelectric switch is used as the detection area. When the light intensity of the light emitting element 1 is enhanced and the output of the photodetector is amplified to a high degree, the detection area is extended to a longer distance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a diffuse reflection type photoelectric switch characterized by a lens structure provided in a light emitting/receiving section.

[Summary of the invention]

In the photoelectric switch according to the present invention, the lens used in the light emitting/receiving section is formed as a Fresnel lens consisting of a plurality of partial lenses having different eccentricities and radii of curvature depending on the position of the lens surface, and the lens is used to emit and receive light. This is a diffuse reflection type photoelectric switch that can detect objects from close range to long distance by expanding the detection range.

[Prior art and its problems]

In the conventional diffuse reflection type photoelectric switch, as shown in FIG. The object is detected when the light from the object is irradiated onto the object and applied to the light receiving section 6. In such a conventional diffuse reflection type photoelectric switch, the lens 3.4 of the light emitting/receiving section
A spherical or aspherical lens is used for the photoelectric switch, and the object detection area of the photoelectric switch is set to an area where the range of light emitted from the light projecting unit 5 and the light receiving range of the light receiving unit 6 overlap, as shown in FIG. It had been. When the area near the photoelectric switch is used as the detection area, the light emitting/receiving section 5.6 is arranged so that the light emitting element 1 and the light receiving element 2 are arranged outside the optical axis as shown in FIG. In addition, when the detection area is a region far away from the photoelectric switch, the light emitting/receiving element 1.2 can be placed at a position approximately equal to the optical axis as shown in FIG. 6(b). In addition, in order to detect objects at close range, the light emitting element 1 and the light receiving element 2 are configured to be significantly offset from the optical axis as shown in Fig. 6 (C). There is also.

However, conventional photoelectric switches have a problem in that a single photoelectric switch cannot simultaneously detect objects from close range to long distance. In addition, conventional photoelectric switches use spherical or aspherical lenses, so the lenses are thick and
Since the light emitting and receiving elements are arranged near the focal length of the photoelectric switch, it has been difficult to miniaturize the photoelectric switch itself.

[Purpose of the invention]

The present invention has been made in view of the problems of conventional diffuse reflection type photoelectric switches, and it is an object of the present invention to provide a photoelectric switch that can detect areas ranging from close range to long distance. purpose.

[Structure and effects of the invention]

The present invention is a diffuse reflection type photoelectric switch that irradiates a detection area with light and detects an object by the reflected light from the object,
A first Fresnel lens consisting of a plurality of partial lenses each having a different eccentricity and radius of curvature depending on the position of the lens surface, and a light projecting element disposed at a focal position of the first Fresnel lens. , a light projection unit that emits a light beam that irradiates light to a different area by each partial lens of the first Fresnel lens, and a plurality of partial lenses each having a different eccentricity and radius of curvature depending on the position of the lens surface. a second Fresnel lens, and a light-receiving element placed at the focal point of the second Fresnel lens, which overlaps the irradiation area of the light projecting unit and allows each partial lens of the second Fresnel lens to illuminate a different area. The device is characterized by comprising a light receiving section that collects light.

According to the present invention having such characteristics, the light emitting/receiving section of the photoelectric switch is configured by a Fresnel lens using a plurality of partial lenses having different eccentricity and radius of curvature depending on the position of the lens surface.

Since the irradiation area and light-receiving area of each partial lens of each Fresnel lens are made different, a light emitting/receiving section is configured that irradiates light to an arbitrary area or receives light from an arbitrary area. Therefore, the detection area can range from close range to long distance. Furthermore, since the lens thickness is significantly reduced compared to conventional lenses, it is possible to downsize the optical system and the photoelectric switch itself. In addition, the thickness of the lens becomes uniform and its shaping becomes easy, so that the cost can be reduced.

[Explanation of Examples]

FIG. 1 is a partially cutaway sectional view showing an embodiment of a photoelectric switch according to the present invention. In the diffuse reflection type photoelectric switch of this embodiment, Fresnel type lenses 12 and 13 are provided in front of the light projecting section 10 and the light receiving section 11. Since the Fresnel lenses 12, 13 according to the invention are identical, the Fresnel lens 12 will be described below. The Fresnel lens 12 is formed from partial lenses by dividing a plurality of aspherical lenses according to the axis of the lens, as shown in FIGS. The lenses 12a to 12f constitute a Fresnel lens.Each aspherical lens is usually calculated based on the following formula.

-E R: Radius of curvature E: Eccentricity Here, the Fresnel lens 12 of the present invention has each partial lens 12
It is assumed that lenses a to 12f have different radii of curvature and eccentricity. When the light projecting element 1 such as a light emitting diode is placed at the focal position, each of the partial lenses 12a to 1
The partial lenses are set so that light is irradiated to sequentially bounded areas from 2f without overlapping. For example, as shown in FIG. 3, a substantially parallel light beam is emitted forward from the partial lens 12a, a light beam is slightly spread downward from the partial lens 12b so as not to intersect with the light beam from the partial lens 12a, and a light beam is emitted from the partial lens 12c. ~12'', each partial lens of the Fresnel lens 12 is configured in the same way so that the light beams do not overlap and the irradiation angle is sequentially expanded downward.Similar partial lenses are also configured for the Fresnel lens I3 that constitutes the light receiving section 11. It is assumed that a Fresnel lens having the following is used and the light receiving element 2 is disposed at its focal position.

Using the Fresnel lens configured in this way, the light emitting/receiving section 1
0.11, the Fresnel lens 2 of the light projection unit 10 irradiates light onto different areas as shown in FIG. The light receiving section 11 also focuses light from different light receiving areas from the respective partial lenses 13a to 13f of the Fresnel lens 13 onto the light receiving element 2 disposed at the focal position. Therefore, these intersection areas become the detection area, and the area from the close range to the far distance of the photoelectric switch can be used as the detection area.

Here, by increasing the light intensity of the light projecting element 1 of the light projecting section 10 and amplifying the output of the light receiving element 2 with a high amplification factor, it becomes possible to expand the distant detection area.

In this embodiment, the light beams of the partial lenses 12a and 13a located at the outermost part of the Fresnel lenses 12 and 13 are made almost parallel to the horizontal optical axis of the photoelectric switch, but by expanding these beams to the outside, the light beams can be made wider. It is possible to construct a proximity switch that senses a range of areas.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway sectional view showing an embodiment of the photoelectric switch according to the present invention, and FIG. 2 (al is a sectional view showing an embodiment of the multistage Fresnel lens used in the photoelectric switch of the present embodiment)
Fig. 2 (bl is a front view thereof, Fig. 3 is a diagram showing the light irradiation and light receiving area of the light emitting/receiving section using the Fresnel lens according to this embodiment, and Fig. 4 is a partially cutaway cross section of a conventional photoelectric switch. Figures 5 and 5 are diagrams showing the irradiation light receiving area and the detection area, and Figures 6 (al to 6 (C1) are diagrams showing changes in the detection area with respect to the position of the light emitting/receiving element of a conventional photoelectric switch. Yes. 1-...- Light emitting element 2-...- Light receiving element 5,1
0・---111 Light emitter 6.11---1 Light receiver
12.13---Fresnel lens 12a
〜12f, 13-r,: ,′,1□ Patent applicant Tateishi Electric Co., Ltd. agent Patent attorney Yoshiki Okamoto (and one other person) -・-Kishonboku 12.13------'7 Nehrushin Figure 2 (a) (b) -A Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] (1) In a diffuse reflection type photoelectric switch that irradiates light onto a detection area and detects an object based on the light reflected from the object, the light is detected from multiple partial lenses each having a different eccentricity and radius of curvature depending on the position of the lens surface. a first Fresnel lens, and a light projecting element disposed at a focal position of the first Fresnel lens, and a light beam that irradiates light to different areas by each partial lens of the first Fresnel lens. a second Fresnel lens consisting of a plurality of partial lenses each having a different eccentricity and radius of curvature depending on the position of the lens surface; and a second Fresnel lens arranged at the focal position of the second Fresnel lens. a light receiving element, the light receiving part overlapping the irradiation area of the light projecting part and condensing light from different areas by each partial lens of the second Fresnel lens. .