JPH0526725A - Limited reflection type sensor - Google Patents

Abstract

PURPOSE:To enable detection of an object within a limited long-distance range by providing a light-intercepting plate which covers a part of a light-sensing element sensing a reflected light from the object being present in a limited reflection region. CONSTITUTION:A light-sensible region R is limited to be narrow by providing a light-intercepting plate 10 covering a part of a light-sensing element 12. A mark P shows the right end of the region R in the case when the light- intercepting plate 10 is not provided. In other words, a scattered light in a region shown by a mark N is obstructed by the light-intercepting plate 10 and does not enter the light-sensing element 12. The fore end of the light-intercepting plate 10 is sharpened to be thin so as to eliminate the effect of the thickness thereof. The light-intercepting plate 10 is disposed preferably at a position where a reflected light from an object is imaged on the front of the light-sensing element 12 by a light-sensing lens 8. Thereby it can be avoided that the quantity of light sensed by the light-plate 10. The region R can be limited more by covering the opposite sides of the light-sensing element 12 with two light- intercepting plates. Consequently, a limited reflection region L is limited more as well and only an object inside the more limited region can be detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a limited reflection photoelectric sensor.

[0002]

2. Description of the Related Art FIG. 11 shows an example of a conventional sensor using a two-division PD (photodetector). The light emitted from the light projecting element 104 to the detection target object via the lens 106 is
The light is reflected by the object to be detected, divided into two lights by the lens 108, and is incident on the photodetection elements 112A and 112B of the two-split PD. Photodetector 112
The light incident on A and 112B changes depending on the position of the sensing object. The outputs of the photo detectors 112A and 112B are supplied to the processing circuit 120. Processing circuit 120
Outputs an ON (object detection) signal when the former output is smaller than the latter output, and outputs an OFF signal when the former output is larger than the latter output. When the light receiving elements 112A and 112B receive the reflected light from the position N in FIG. 11, the processing circuit 120 outputs an ON signal, but the light receiving element 1 receives the reflected light from the position M separated from the position N by a certain distance or more.
12A and 112B receive the processing circuit 12
0 does not output an ON signal. Therefore, an object within a certain range can be detected. There is a conventional example in which the two-division PD is replaced with PSD. FIG. 12 shows an example of a conventional photomicrosensor. In this example, an object in a region L where the light irradiation region S formed by the light projecting element 204 and the light projecting lens 206 and the light receivable region R formed by the light receiving lens 208 and the light receiving element 212 overlap is detected. .

[0003]

The sensor using the two-division PD and the sensor using the PSD shown in FIG. 11 are expensive because the light receiving element is expensive and the processing circuit 120 is required. Become.

In the photomicrosensor shown in FIG. 12, the projected beam diameter, that is, the light irradiation area S and the light receivable area R are respectively the light projecting element 204 and the light receiving element 21.
Since it spreads as it goes away from 2, if the distance to the detection target object becomes long, the region L expands infinitely far away as shown in FIG. It is not possible to detect an object within a limited long distance range.

The present invention has been made in view of such a situation, and an object thereof is to provide a limited reflection type sensor capable of detecting an object within a limited long distance range at low cost.

[0006]

According to another aspect of the present invention, there is provided a limited reflection type sensor having a light irradiation area formed by a light projecting optical system including a light projecting element and a light receiving area formed by a light receiving optical system including a light receiving element. A limited reflection type sensor in which a light receiving element receives a reflected light from an object existing in a limited reflection area which is an area where and overlap with each other, and the light receiving element is provided with a light shielding plate which covers a part of the light receiving element. And

In a limited reflection type sensor according to a second aspect of the present invention, a light receiving optical system includes a light receiving lens for forming an image of reflected light from an object on the front surface of the light receiving element, and a light shielding plate is provided at an image forming position of the reflected light from the object. It is characterized by being arranged.

[0008]

In the limited reflection type sensor according to the first aspect of the invention, since the light shielding plate covers a part of the light receiving element, the limited reflection area can be limited to a predetermined range. Can detect objects.

In the limited reflection type sensor according to the second aspect, since the light shielding plate is arranged at the image forming position of the reflected light, the limited reflection area can be limited to a predetermined range without reducing the light receiving amount of the light receiving element. .

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of an embodiment of a limited reflection type sensor of the present invention. Prior to the description of this embodiment, the principle of the limited reflection sensor, which is the premise of the embodiment, will be described with reference to FIG. In the limited reflection type sensor 2 of FIG. 7, the light projecting optical system including the light projecting element 4 and the light projecting lens 6 is in the vertical direction of the drawing, that is, the light receiving lens 8 and the light receiving element 1.
The light receiving lens 8 is configured to receive light directly above it by projecting light obliquely with respect to the optical axis direction of the light receiving optical system composed of two. The limited reflection area L is an area where the light irradiation area S formed by the light projecting optical system and the light receiving area R formed by the light receiving optical system overlap. The limited reflection area L is an area where the sensor 2 can detect an object.

The light irradiation area S and the light receivable area R become wider as the distance from the sensor 2 increases. This spread can be suppressed smaller as the element angle is smaller. For example, the light emitting portion of the light projecting element 4 formed of an LED is 0.5.
In the case of 5 mm square, the spread of the light irradiation region S can be reduced, but the light receiving area of the light receiving element 12 has a large spread because the light emitting portion of the light receiving element 12 is generally 2.1 mm square. Therefore, as shown in FIG. 8A, when the distance from the sensor 2 to the detection position D of the object becomes long, the angle-limited reflection area L becomes large, and a background object other than the object to be detected may be erroneously detected. There is.

When the detection object is a scattering reflector, scattered light from a distance has a weak intensity and thus does not pose a problem. However, as shown in FIG. 9, the sensor 2 is an original detection sensor of the copying machine 20. In some cases, the sensor 2 must have a sensitivity that can detect a dark original document 24 having a low light reflectance shown in FIG. It is erroneously detected as 24.

In the embodiment of the present invention shown in FIG. 1, in order to eliminate such erroneous detection, a light shielding plate 10 which covers a part of the light receiving element 12 is provided. The light-shielding plate 10 limits the light-receivable region R to be narrow as shown in FIGS. 1 and 2. Reference numeral P in FIG.
Indicates the right end of the light receivable region R when the light shielding plate 10 is not provided. That is, the scattered light in the area indicated by the reference numeral N is blocked by the light shielding plate 10 and does not enter the light receiving element 12. The light-shielding plate 10 has a thinly pointed tip in order to eliminate the influence of its thickness.

FIG. 3 shows the operation of the shading plate 10 in more detail. The area indicated by reference numeral P equivalently functions as a scattering light source when an object reflects a small projection beam emitted from a projection optical system including a projection element 4 and a projection lens 6. The light from the side indicated by reference numeral Q is provided with the light shielding plate 10, so that the light receiving element 12
Does not enter.

The light shield plate 10 is preferably arranged at a position where the reflected light from the object is imaged on the front surface of the light receiving element 12 by the light receiving lens 8. By doing so, it is possible to avoid a decrease in the amount of light received by the light receiving element 12 due to the light shielding plate 10.
FIG. 4A shows a state of light when the light shielding plate 10 is closer to the light receiving lens 8 with respect to the image forming position, and FIG.
FIG. 4C shows a state of light when the light shielding plate 10 is at the same position as the image forming position, and FIG. 4C shows a state of light when the light shielding plate 10 is on the opposite side of the light receiving lens with respect to the image forming position. Show. Figure 4
In any of (a), (b), and (c), the light shielding plate 10 is arranged so that the width of the light-receivable area becomes equal at the object detection position. In the case of FIG. 4B, all the light from the object, that is, the scattered light source passes without being blocked by the light blocking plate 10, but in the cases of FIGS. 4A and 4C, the light is the light blocking plate 10. Part of the light is blocked by the light, and the amount of light received by the light receiving element 12 decreases. That is, only in the case of FIG. 4B, the light receivable region R can be limited without loss of the amount of light received.

5 and 6 show another embodiment of the limited reflection type sensor of the present invention. In this embodiment, the two light shields 10A and 10B cover not only one side of the light receiving element 12 but also the other side. Reference numeral A in FIG. 5 indicates the right end of the light receivable region R when the light shielding plate 10A is not provided, and is the same as reference numeral P in FIG. Reference symbol B indicates the left end of the light-receivable region R when the light shielding plate 10B is not provided. That is, the light blocking plate 10B has a light receiving region R
The projection optical system side of is limited. Therefore, by providing not only the light shielding plate 10A but also the light shielding plate 10B, the light receiving area R can be more limited, and the limited reflection area L is also more limited. Therefore, only the objects within the more limited area can be obtained. Can be detected.

[0017]

As described above, according to the limited reflection type sensor of claim 1, since the light shielding plate is configured to cover a part of the light receiving element, the limited reflection area can be limited to a predetermined range. It is possible to detect an object within a long distance range limited by cost.

According to the limited reflection type sensor of the second aspect, since the light shielding plate is arranged at the image forming position of the reflected light, the limited reflection area can be limited to a predetermined range without reducing the amount of light received by the light receiving element.

[Brief description of drawings]

FIG. 1 is an optical configuration diagram showing a configuration of an embodiment of a limited reflection type sensor of the present invention.

FIG. 2 is a perspective view showing the embodiment of FIG. 1 in three dimensions.

3 is an optical path diagram showing the function of the light shielding plate 10 of FIG. 1 in more detail.

FIG. 4 is an optical path diagram showing a change in light when the position of the light shielding plate 10 in FIG. 1 is changed.

FIG. 5 is an optical configuration diagram showing a configuration of another embodiment of the limited reflection type sensor of the present invention.

FIG. 6 is a perspective view showing the embodiment of FIG. 5 in three dimensions.

FIG. 7 is an optical configuration diagram showing a configuration of a limited reflection sensor which is a premise of the embodiments of FIGS. 1 and 5.

8 is an optical path diagram showing a change in a limited reflection area L when an object detection position of the limited reflection sensor in FIG. 7 changes.

9 is a front view showing an example in which the limited reflection type sensor of FIG. 7 is used in a copying machine.

10 is an explanatory diagram showing a relationship between a limited reflection area and a document and a document retainer in the example of FIG.

FIG. 11 is an optical configuration diagram showing an example of a sensor using a conventional two-division PD.

FIG. 12 is an optical configuration diagram showing an example of a conventional photomicrosensor.

[Explanation of symbols]

4 Projection element 6 Projection lens 8 Light receiving lens 10, 10A, 10B light shield 12 Light receiving element L limited reflection area

Claims (2)

[Claims] 1. An object existing in a limited reflection area, which is an area where a light irradiation area formed by a light projecting optical system including a light projecting element and a light receivable area formed by a light receiving optical system including a light receiving element overlap each other. A limited reflection type sensor, wherein the light receiving element receives the reflected light to detect the object, the limited reflection type sensor comprising a light shielding plate that covers a part of the light receiving element. 2. The light-receiving optical system includes a light-receiving lens for forming an image of reflected light from the object on the front surface of the light-receiving element, and the light-shielding plate is arranged at an image-forming position of the reflected light. The limited reflection type sensor according to Item 1.