JPH04259829A - Transmission-type sensor - Google Patents

Abstract

PURPOSE:To obtain a transmission-type stable sensor without erroneous detection which can obtain the same output of a photodetector even when a light bending member is shifted as when it is not shifted. CONSTITUTION:A transmission-type sensor 10 is constituted of a detector 1 which is comprised of a light emitting element 4 and a photodetector 5 arranged in parallel to the element 4, and a light bending member 11 confronting to the detector 1. The light bending member 11 guides the light from the light emitting element 4 to the photodetector 5. The bending member 11 is a triangular prism in an isosceles triangular cross section with 22.5 deg. base angle, having superior transmittance. A base 11c confronts to the detector 1 with a predetermined distance. Moreover, the two equilaterals 11a, 11b of the member 11 are mirror finished.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission type sensor that detects the presence or absence of an object using a detector equipped with a light emitting element and a light receiving element, and a light bending member facing the detector.

0002

2. Description of the Related Art FIG. 6 is an explanatory diagram of the structure and operation of a conventional transmission type sensor. In the figure, numerals 1 and 2 are a detector and a prism (light bending member) which are arranged opposite to each other with a conveyance path 3 in between.

The detector 1 includes a light emitting element 4 and a light receiving element 5.
They are arranged in parallel so that their optical axes are parallel. Prism 2 is
It is for bending the light from the light emitting element 4 to the light receiving element 5, and its base 2a faces the detector 1 at a predetermined distance.

[0004] The light output from the light emitting element 4 is bent by the prism 2 as shown by the arrow line and is received by the light receiving element 5. When an object 100 such as paper is conveyed along the conveyance path 3 as shown by the arrow and blocks the optical path, the light receiving element 5
The output is no longer present, and the entry of the object 100 is detected.

[0005]

[Problems to be Solved by the Invention] In such a conventional system, if the prism 2 deviates from its normal position indicated by the dotted line in FIG. 7 to the position indicated by the solid line, the light is no longer received by the light receiving element 5. The situation is the same as when an object is present, causing false detection such as there being an object to be detected even though there is no object to be detected.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a stable transmission type sensor that is free from false detection and can obtain the same output from a light receiving element even when a light bending member is misaligned as when the light bending member is not misaligned.

[0007]

[Means for Solving the Problems] In order to achieve the above object, in the present invention, a detector including a light emitting element and a light receiving element arranged side by side has an isosceles triangular cross section with a base angle of 22.5°. A triangular prism-shaped light bending member with excellent transmittance for guiding light from the light emitting element to the light receiving element is arranged such that the bottom side of the light bending member faces the detector at a predetermined distance. The structure (first structure) is characterized in that two equal sides of the light bending member are each subjected to a mirror finish. Further, a detector including a light emitting element and a light receiving element arranged side by side is provided with a light bending element for guiding light from the light emitting element to the light receiving element. The first and third mirror-like pieces are two virtual triangular prisms each having an isosceles triangular cross section with a base angle of 22.5° and whose base faces the sensor at a predetermined distance. The second mirror-shaped piece is arranged equilaterally, and
A configuration (second configuration) characterized in that the mirror is disposed on the base between the first and third mirror-like pieces.

[0008]

[Operation] In the case of the first configuration, the light output from the light emitting element passes through the bottom side of the light bending member, is reflected by one of the equilateral mirror-finished parts, and is directed toward the bottom side. The light towards the bottom is
Since the base angle of the isosceles triangle is 22.5°, total reflection occurs at the base. The totally reflected light is reflected by the other equilateral mirror-finished portion and is received by the light receiving element. In addition, in the case of the second configuration, the light output from the light emitting element is
It is reflected by a first mirror-like piece on one equilateral side of the virtual triangular prism, toward the base, and is reflected by a second mirror-like piece on the base. The reflected light is directed toward the other equal side, is reflected by the third mirror piece, and is received by the light receiving element. In each of these sensor configurations, even if a positional shift occurs in the light bending member, the incident light on the light receiving element passes through the same optical path. This is because the base angle of the isosceles triangle is 22.5°. Therefore, a stable sensor that does not cause false detection even if a positional shift occurs in the light bending member can be obtained. Although the second configuration has a drawback that the allowable value for the positional deviation of the light bending member is somewhat narrow, it is advantageous in terms of cost.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 5.

A first embodiment is shown in FIGS. 1 to 3.

FIG. 1 is an explanatory diagram of the configuration and operation of a transmission type sensor 10 of this example, and in the figure, 11 is a light bending member. The light bending member 11 is made of glass, plastic, etc. with excellent transmittance, and has a base angle of 22.5° as shown in FIG.
It has a triangular prism shape with an isosceles triangular cross section. The two equal sides 11a and 11b of the light bending member 11 are mirror-finished, so that light can be reflected efficiently. Further, the bottom side 11c is a flat surface so that light can easily pass through. This transmission type sensor 10 is
The bottom side 11c is arranged so as to face the detector 1 at a predetermined distance. The operation of this transmission type sensor 10 is as follows.

[0012] The light output from the light emitting element 4 is
Transmitted through point a of c and reflected at point b on equilateral side 11a (β=6
7.5°) and heads toward point c on the bottom surface 11c. Since the base angle α is 22.5°, the light directed toward point c is totally reflected at point c (γ=45°) and travels toward point d on equilateral side 11b. The light directed toward point d is reflected in the same way as point b, and is received by the light receiving element 5. If an object to be detected enters the conveyance path 3 and blocks the optical path, the light received by the light receiving element 5 decreases, so it is possible to know the presence or absence of an object to be detected, similar to the conventional prism method. .

As shown in FIG. 3, when the light bending member 11 is shifted from the normal position indicated by the dotted line to the position indicated by the solid line, the light output from the light emitting element 4 is reflected at point b' of the equal side 11a and is reflected at the base 11c. towards point c'. The light heading towards point c' is c
It is totally reflected at point ' and goes to point d' on the equal side 11b. The light directed to point d' is reflected in the same way as point b', but this light is
The light passes through the same optical path as the optical path reflected at point d before the positional shift occurs. The dotted arrow line indicates the path of light when no positional shift occurs. In this way, even if the light bending member 11 is misaligned, the same light receiving element output as when the light bending member 11 is not misaligned can be obtained. That is, it is possible to prevent false detection and achieve stability.

A second embodiment is shown in FIGS. 4 and 5.

FIG. 4 is an explanatory diagram of the configuration and operation of the transmission type sensor 20 of this example, and in the figure, 21 is a light bending member. The light bending member 21 includes first, second, and third mirror pieces 22, 2
It consists of 3,24. first and third mirror pieces 22,
24 is arranged on equilateral sides 25a and 25b of a virtual triangular prism 25 (the space surrounded by a dotted line in the figure) having an isosceles triangular cross section with a base facing the detector 1 at a predetermined distance and a base angle of 22.5°. The second mirror-like piece 23 is arranged on the bottom side 25c between the first and third mirror-like pieces 22 and 24. The operation of this transmission type sensor 20 is as follows.

FIG. 4 where there is no misalignment of the light bending member 21
In the case of , the light is reflected at points b, c, and d on each mirror piece and is received by the light receiving element 5, and has the same function as in FIG. When the position of the light bending member 21 shifts, as shown in FIG. 5, if the amount of shift is small, it is the same as in FIG.
When the positional deviation becomes large to a certain extent, the light is not reflected at point c' and the optical path is cut off, so that the light does not reach the light receiving element 5. In other words, there will be paper present. As described above, although the method of this example has the drawback that the allowable value for deviation is somewhat narrow, it is advantageous from a cost perspective.

[0017]

As described above, according to the present invention, even if the light bending member is misaligned, the same light receiving element output can be obtained as when the light bending member is not misaligned, and a stable sensor without false detection can be obtained. Obtainable.

[Brief explanation of the drawing]

FIG. 1: Configuration of a transmission type sensor according to a first embodiment of the present invention;
It is an action explanatory diagram.

FIG. 2 is a perspective view showing the shape of the light bending member according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of the effect of the transmission type sensor according to the first embodiment of the present invention.

FIG. 4 shows the configuration of a transmission type sensor according to a second embodiment of the present invention;
It is an action explanatory diagram.

FIG. 5 is an explanatory diagram of the effect of the transmission type sensor according to the second embodiment of the present invention.

FIG. 6 is a diagram illustrating the configuration and operation of a conventional transmission type sensor.

FIG. 7 is a diagram illustrating problems with a conventional transmission type sensor.

[Explanation of symbols]

1 Detector 3 Transport path 4 Light emitting elements 10, 20 Transmissive sensors 11, 21 Light bending members 11a, 11b, 25a, 25b Equal sides 11c,
25c Base 22, 23, 24 Mirror piece

Claims (2)

[Claims] 1. A detector (1) comprising a light-emitting element (4) and a light-receiving element (5) arranged side by side is provided with the above-mentioned sensor having excellent transmittance and having an isosceles triangular cross section with a base angle of 22.5°. Light emitting element (4
A triangular prism-shaped light bending member (11) for guiding light from the light receiving element (5) to the light bending member (
The base (11c) of the light bending member (11) is arranged to face the detector (1) at a predetermined distance, and the two equal sides (11a, 11b) of the light bending member (11) are each mirror-finished. A transmission type sensor that is characterized by the 2. A detector (1) consisting of a light emitting element (4) and a light receiving element (5) arranged side by side, and a detector (1) consisting of first, second and third mirror pieces (22, 23, 24). The light emitting element (4
) are arranged opposite to each other for guiding light from the light receiving element (5) to the light receiving element (5), and the first and third mirror pieces (22, 24) have a base (25c). disposed on two equilateral sides (25a, 25b) of a virtual triangular prism (25) that faces the detector (1) at a predetermined distance and has an isosceles triangular cross section with a base angle of 22.5°; The mirror-like piece (23) is the first and second mirror-like piece (22, 24).
A transmission type sensor, characterized in that it is arranged on the bottom side (25c) in the middle of the .