JP2003294413A - Optical detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical detector capable of performing stable detection without being affected by a background or the like. <P>SOLUTION: A diffusion reflection type photoelectric sensor 10 includes the light cut-off plate 24 arranged between a light detection element 22 and a light detection lens 26, and a slit 30 is formed to the light cut-off plate 24. The projection light emitted from the sensor 10 forms a detection area flatly spreading within one plane, but the range of the distance L2 from a point spaced apart from the sensor 10 by a distance L1 in this detection area becomes a substantial detection area, that is, a reaction region 34 (the area shown by an oblique line in Fig) and an area other than that area becomes an insensitive region. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to optical detectors such as photoelectric sensors.

[0002]

2. Description of the Related Art There is known an optical detector that emits light toward a detection object and detects the presence or absence of the detection object from the reflected light. It is a diffuse reflection photoelectric sensor. The diffuse reflection photoelectric sensor is
There are various types such as a limited reflection type that applies a light beam to the detection object and an area spot reflection type that applies light that spreads flatly in one plane to the detection object. Being developed.

FIG. 1 shows the basic structure of a limited reflection photoelectric sensor. The limited reflection photoelectric sensor 1 determines a light projecting circuit 3 arranged in a case 2, a light projecting element 4 controlled by the light projecting circuit 3, a light receiving element 5 that receives reflected light, and whether light is received. Then, when the photoelectric sensor 1 is receiving light, the operation indicator lamp 7 is turned on.

This limited reflection type photoelectric sensor 1 has a light projecting lens 8 disposed adjacent to the light projecting element 4, and emits a thin thread-like light beam toward the detection body T through the light projecting lens 8. To do. As a result, a part of the diffusely reflected light from the detection body T enters the light receiving element 5 through the light receiving lens 9,
In order to prevent the detection accuracy from decreasing due to the background, the detection object T
A light-shielding plate S having a diaphragm or a small hole is typically provided between the light-receiving lens 9 and the light-receiving element 5 so that only light reflected from the light-receiving element 9 enters the light-receiving element 9. Has been done.

[0005]

However, in the limited reflection photoelectric sensor, the displacement (positional deviation) of the detection body T from a predetermined position, the change of the passing position of the detection body T, the change of the inclination, and the detection body T are detected. Since it is sensitive to changes in shape or size, subtle setting work is required to ensure stable detection, and maintenance for avoiding malfunction due to deviation of the optical axis after setting. It has the drawback of requiring a great deal of effort.

On the other hand, in the above-mentioned area spot reflection type photoelectric sensor, since the light which spreads flatly is applied to the detection object T, the positional deviation of the detection object, the change of the passing position or the size of the detection object is detected. Although it is possible to reliably detect without being affected by changes, etc., if there is an object with high surface gloss near the background or the detection object, the reflected light from this object will be received. have.

Therefore, the purpose of the present invention is to influence the background and
Displacement (displacement) of the detection object from a predetermined position, detection object T
An object of the present invention is to provide an optical detector capable of performing stable detection without being affected by changes in the passing position, changes in the inclination, changes in the shape or size of the detection body T, and the like.

Another object of the present invention is to provide an optical detector capable of eliminating the drawbacks of the limited reflection type while maintaining the advantages thereof.

Another object of the present invention is to provide an optical detector capable of eliminating the drawbacks of the area spot reflection type while maintaining the advantages thereof.

Still another object of the present invention is to provide an optical detector capable of limiting the distance of a detectable area.

Still another object of the present invention is to provide an optical detector capable of limiting the width of a detectable area extending in one plane.

[0012]

According to the present invention, such a technical problem is an optical detector having a detection area that spreads flat in one plane and receives diffused reflected light from a detection body. And a light-shielding means disposed in front of the light-receiving means of the optical detector, wherein the light-shielding means has a slit that limits a part of the fan-shaped detection area to a substantial detection area, This is achieved by providing an optical detector characterized in that the slit forms the substantial detection area at a distance L2 from a point L1 distant from the optical detector.

[0013]

According to a preferred embodiment of the present invention, the slit has a length and a width, and the length of the slit allows detection of a reaction region in which a detection object can be detected in the detection area. Distances L1 and L2 are defined.

The present invention is most typically a diffuse reflection photoelectric sensor. The photoelectric sensor includes a light receiving element, and a light shielding plate having a slit is arranged in front of the light receiving element. Instead of the light-shielding plate having the slit, the slit may be formed in the partition wall arranged in the case so that the partition wall realizes the function of the light-shielding plate.

The above objects, other objects and functions of the present invention,
The effects will be apparent from the detailed description of the examples below.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

Referring to FIG. 2, the diffuse reflection photoelectric sensor 10 of the embodiment has a light projecting circuit and a light receiving circuit (both not shown) housed in a case 12 and emits light as in the conventional case. A laser diode 14 is provided as an element. The sensor 10 includes two light projecting lenses 16 and 18 arranged side by side in the optical axis direction. The light emitted from the laser diode 14 becomes a spot-shaped light beam through the first light projecting lens 16 adjacent to the laser diode 14, and this spot-shaped light beam is similar to the conventional area spot reflection type photoelectric sensor. Then, by passing through the second light projecting lens 18, it becomes light that spreads flat in one plane in the vertical direction with respect to the paper surface of FIG.
Is released to the outside through. The way in which the light spreads in one plane may be a fan shape that widens toward the end as shown in the figure, or may be a band shape having a certain width.

The diffuse reflection photoelectric sensor 10 of the embodiment also has a light receiving element 22 at a position separated from the laser diode 14, and a light shielding plate 24 and a light receiving lens 26 are arranged in this order in front of the light receiving element 22. Has been done.

The reflected light passes through the light receiving lens cover 28 and the light receiving lens 26, and then only the light that passes through the slit 30 (described later) of the light shielding plate 24 is received.
Enter into.

FIG. 3 shows the slit 30 of the light shielding plate 24.
It is the figure which looked at from the front. Although FIG. 3 is a view of a part of the light shielding plate 24 viewed from the front, the slit 3
In order to clearly show the existence of 0, the plate surface portion of the light shielding plate 24 is shown by hatching. The slit 30 is
The slit 30 has an elongated rectangular shape having a height H and a width W and extends in a straight line. The slit 30 extends vertically along the plane of the drawing, as described with reference to FIG.

FIG. 4 shows a diffuse reflection photoelectric sensor 1 of the embodiment.
It is a figure for demonstrating the detection area of 0. The light projection 32 emitted from the sensor 10 forms a detection area that is flat and fan-shaped and spreads in a single plane, and in this detection area, the range from the point separated from the sensor 10 to the distance L1 is substantially present. The target detection area, that is, the reaction area 34 (hatched area), and the other areas are dead areas. The distance L2, which is the depth of the reaction region 34, is defined by the height H of the slit 30 of the light shielding plate 24 (FIG. 5), and the substantial width w of the detection area 34 is defined by the width W of the slit 30. To be done. That is, the reflected light that passes through the slit 30 of the light blocking plate 24 and enters the light receiving element 22 is limited to the reaction region 34, and the reflected light in other areas is the light blocking plate 2.
Eliminated by 4.

From the above, the diffuse reflection photoelectric sensor 10 of the embodiment has the following characteristics. That is,
Like the conventional area spot type photoelectric sensor, the diffuse reflection type photoelectric sensor 10 has a detection area that spreads flat in one plane (in this embodiment, the detection area spreads in a fan shape that spreads toward the end). The vertical slit 30 of the light shielding plate 24 arranged in front of the light receiving element 22 defines the substantial detection area, that is, the width w and the distance L2 of the reaction region 34.

Therefore, by adjusting the height H and width W of the slit 30 of the light shielding plate 24, the reaction region 3
The width w and the distance L2 of 4 can be freely set.
Moreover, by adding a variable mechanism capable of adjusting the height H and / or the width W of the slit 30, the user can freely adjust the reaction region 34.

According to the photoelectric sensor 10 having the above characteristics, even if an object having a high surface gloss is present in the vicinity of the background or the detection body T, stable detection is performed without being affected by the object. be able to. Further, since the presence or absence of the detection body T is detected by averaging the amount of light received in the reaction area of the substantially rectangular plane, there are variations in the size and / or shape of the detection body T and variations in the passing position of the detection body T. Even if
It can be detected stably.

FIG. 5 is a diagram for explaining the change in the amount of received light when the range of 40 mm to 80 mm from the sensor 10 is set in the reaction area 34. As can be understood from the figure, in the reaction area 34, Since the amount of received light changes significantly with respect to the detection distance direction, this characteristic can be used to detect not only the presence or absence of the detection object T in the reaction region 34 but also a minute step. it can.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to this. For example, in the above embodiment, between the light receiving element 22 and the light receiving lens 26,
Although the light shielding plate 24 having the slit 30 is arranged,
The partition 32 arranged in the case 12 of the sensor 10, that is, the partition 32 that partitions the various lenses 16, 26 and the like from the light emitting element 14 and the light receiving element 22 is formed with a vertically long hole 30a that exhibits the same function as the slit 30. By doing so, the function of the light shielding plate 24 may be exerted by the partition wall 32.

Further, in the above embodiment, the sensor 10 which outputs an ON / OFF signal to the outside according to the amount of light received by the light receiving element 22 is exemplified, but a CCD camera is arranged instead of the light receiving element 22. Alternatively, according to this, information such as the shape of the detection body T may be detected.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a conventional limited reflection photoelectric sensor.

FIG. 2 is a schematic configuration diagram of a diffuse reflection photoelectric sensor according to an embodiment.

FIG. 3 is a partial front view of the light shielding plate for explaining a slit formed in the light shielding plate arranged in front of the light receiving element.

FIG. 4 is a diagram for explaining a substantial detection area of the diffuse reflection photoelectric sensor of the embodiment.

FIG. 5 is a characteristic diagram of the diffuse reflection photoelectric sensor of the example, and is a diagram for explaining the relationship between the detection distance and the amount of received light.

[Explanation of symbols]

10 Diffuse reflection type photoelectric sensor 12 sensor case 14 Laser diode 22 Light receiving element 24 Shading plate 26 Light receiving lens 30 slits 34 Substantial detection area (reaction area) H slit height W slit width Distance from L1 sensor to reaction area L2 reaction area detection distance w Width of reaction area

Claims (4)

[Claims] 1. An optical detector that has a detection area that spreads flat in one plane and that receives diffused reflected light from a detection body, and is arranged in front of the light receiving means of the optical detector. And a slit that limits a part of the detection area that spreads flat in the one plane to a substantial detection area, and the slit separates from the optical detector. Point L
1. The optical detector, wherein the substantial detection area is formed at a distance L2 from 1. 2. The slit has a length and a width, and the detection distances L1 and L2 of a reaction region capable of detecting a detection object in the detection area depending on the length of the slit.
The optical detector according to claim 1, wherein the width of the reaction region is defined by the width of the slit. 3. The optical detector according to claim 1, wherein the optical detector is a diffuse reflection photoelectric sensor, and the light shielding means is a light shielding plate. 4. The optical detector is a diffuse reflection photoelectric sensor, and a partition located between the light receiving means and a light receiving lens in front of the diffuse reflection photoelectric sensor is disposed in the case of the diffuse reflection photoelectric sensor. The slit is formed in the partition wall, and the partition wall constitutes the light shielding means.
Alternatively, the optical detector according to item 2.