JPH0829161A - Light direction converter and photoelectric switch using it - Google Patents

Abstract

PURPOSE:To provide a light direction converter which can bend in the advancing direction the light while achieving a desired convergence light, and securing a sufficient quantity of light. CONSTITUTION:A prism lens 10 is provided with a first incidence/emission surface 11 for applying light to the inside or emitting light to the outside, a second incidence/emission surface 12 for emitting light to the outside or applying light to the inside, and a reflection surface 13. A first convex lens 14 is formed in one piece on the first incidence/emission surface 11 and a second convex lens 15 is formed in one piece on the second incidence/emission surface 12. Diffusion light emitted from the tip of an optical fiber 40 is converged into parallel light or diffusion light closer to it by the first convex lens 14 and is bent nearly at right angle by the reflection surface 13. The reflection light is further converged by the second convex lens 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light redirecting device for changing the traveling direction of light and a photoelectric switch using the same.

[0002]

2. Description of the Related Art Conventionally, photoelectric switches that detect the presence or absence of an object by utilizing the transmission or reflection of light have been used. When such a photoelectric switch is installed at a place distant from the detection point, light is normally guided from the detection point to the photoelectric switch using an optical fiber. In that case,
If the detection location is narrow, the tip of the optical fiber may be bent and used. However, if the optical fiber is bent with a small bending diameter, light transmission loss occurs, so
The bending diameter cannot be made too small.

In view of this, an optical fiber detection end structure as shown in FIG. 6 is proposed in Japanese Utility Model Laid-Open No. 64-26707. In FIG. 6, an optical fiber 62 and a reflector 63 are inserted in a holding sleeve 61. The reflector 63 is provided with a reflecting surface 64 that is inclined by approximately 45 ° with respect to the axial direction of the holding sleeve 61. Further, a window hole 65 is provided on the side surface of the holding sleeve 61.

The light emitted from the tip of the optical fiber 62 is bent at a substantially right angle by the reflection surface 64 of the reflector 61, and emitted from the window hole 65 to the outside of the holding sleeve 61. In this way, the traveling direction of the light emitted from the optical fiber 62 is approximately 90 °.
Be bent.

However, the light emitted from the optical fiber 62 becomes diffused light which spreads forward with the optical axis as the center. Therefore, part of the light is not reflected by the reflecting surface 64, or the light reflected by the reflecting surface 64 is also emitted as diffused light. As a result, the transmission loss of light becomes large, and a sufficient amount of light cannot be obtained on the light receiving side.

On the other hand, Japanese Utility Model Publication No. 62-35237 proposes an optical transmission device as shown in FIG. In FIG. 7, a recess 73 into which a tip of an optical fiber 72 is fitted is provided at one end of a converter 71 formed by integrally molding a light conductor such as plastic into a rod shape.
Are formed. A recess 75 having an inclined reflecting surface 76 is provided at the other end of the converter 71.

The light emitted from the tip of the optical fiber 72 is condensed by the convex lens 74 and is bent at a substantially right angle by the reflecting surface 76. In this way, the diffused light emitted from the tip of the optical fiber 72 is corrected to convergent light.

Further, Japanese Patent Laid-Open No. 4-225306 proposes an optical axis conversion device as shown in FIG. FIG.
In the cylindrical cap 81, the cylinder lens 8
2 is stored, and the optical fiber 83 is attached to one end of the cap 81.
Has been inserted. The upper end of the cylinder lens 82 is cut at an angle of about 45 ° with respect to the axial direction to form a reflecting surface 84. A convex lens 85 is formed on the side of the cylinder lens 82. A circular hole into which the convex lens 85 is fitted is formed in the cap 81. Also,
A lid member 86 is fitted on the upper end of the cap 81.

The light emitted from the tip of the optical fiber 83 is bent at a substantially right angle by the reflecting surface 84 of the cylinder lens 82, condensed by the convex lens 85 and emitted to the outside. As a result, the diffused light emitted from the optical fiber 83
It is corrected to convergent light by 5.

Incidentally, Japanese Utility Model Laid-Open No. 62-131336 discloses an attachment for a photoelectric switch having a structure similar to that of the optical axis converter shown in FIG.

[0011]

However, since the optical fiber has a diameter of a certain size, the light emitted from the tip of the optical fiber does not become point emission but actually surface emission. Therefore, the spread of the light emitted from the optical fiber becomes considerably large. Therefore, even if the light emitted from the optical fiber 72 is condensed by the convex lens 74 as shown in FIG. 7, or the light reflected by the reflecting surface 84 is condensed by the convex lens 85 as shown in FIG. However, the current situation is that the diffused light cannot be narrowed down to a sufficiently converged light, and a sufficient amount of light cannot be obtained.

Particularly, in the limited reflection type photoelectric switch, unless the beam spot is narrowed down, the detection range and the response become large, and good characteristics cannot be obtained. Here, the limited reflection type photoelectric switch is for detecting the presence or absence of an object at a position separated by a predetermined distance by projecting light and receiving the reflected light.

Therefore, an object of the present invention is to provide a light redirecting device and a photoelectric switch using the same, which can bend the traveling direction of light while realizing desired converged light and securing a sufficient light amount. Is to provide.

[0014]

In order to achieve the above object, the present inventor first analyzed in detail the cause of the problems in the prior art.

As shown in FIGS. 9 (a) and 9 (b), consider a case where a convex lens 92 is formed on the entrance / exit surface of the prism 93 on the optical fiber 91 side. In this case, as shown in FIG. 9A, if the radius of curvature of the convex lens 92 is large, the beam emitted from the optical fiber 91 cannot be sufficiently narrowed. In order to sufficiently narrow the beam, it is necessary to reduce the radius of curvature of the convex lens 92 as shown in FIG. 9B. However, in this case, a part of the diffused light emitted from the optical fiber 91 is converted into a convex lens 92
Reflected on the surface of the and escapes. As a result, the effective diameter acting as a lens becomes smaller than the actual diameter of the convex lens 92, and it is difficult to secure a sufficient amount of light.

As shown in FIG. 9C, the prism 93
Consider the case where the convex lens 94 is formed on the entrance / exit surface of the two entrance / exit surfaces opposite to the optical fiber 91. In this case, when the diameter of the convex lens 94 is small, part of the reflected light of the prism 93 does not enter the convex lens 94. As a result, a sufficient amount of light cannot be secured. On the contrary, if the diameter of the convex lens 94 is increased, the size of the prism 93 itself must be increased, which hinders downsizing of the device.

Therefore, if the tip of the optical fiber 91 is brought closer to the entrance / exit surface of the prism 93 while keeping the diameter of the convex lens 94 small, the amount of light incident on the convex lens 94 can be increased.

However, as shown in (d) and (e) of FIG. 9, when the image is formed at the focus position F which is separated from the convex lens 95 by a certain distance, the tip of the optical fiber 91 is separated from the convex lens 95. In this case, the beam diameter at the focal point F of the optical system can be narrowed down. In the case of FIG. 9E, the radius of curvature of the convex lens 95 can be made larger than that in the case of FIG. 9D. In order to make the characteristics of the photoelectric switch sensitive, it is important that the beam diameter can be narrowed.

For the above reasons, in the prior art,
It is considered that both the desired converged light and a sufficient amount of light could not be satisfied. Therefore, the present inventor created the following present invention based on the above analysis results.

(1) First Invention A light redirecting device according to the first invention is a prism having an incident surface for guiding light therein, an exit surface for emitting light outside, and a reflecting surface for reflecting light, and a prism. A first convex lens provided on the incident surface side of the prism and a second convex lens provided on the exit surface side of the prism, and light incident on the inside of the prism through the first convex lens is reflected on the reflecting surface, The light is emitted through the second convex lens.

(2) Second invention In the light redirecting device according to the second invention, in the configuration of the light redirecting device according to the first invention, the light incident on the incident surface by the first convex lens is substantially parallel. The second convex lens is a lens for converting the light emitted from the emission surface into a convergent light.

(3) Third Invention A photoelectric switch according to a third invention is a photoelectric switch which detects the presence or absence of an object by projecting the light onto the object and receiving the reflected light, and guides the light inside. A prism having an entrance surface, an exit surface for emitting light to the outside, and a reflecting surface for reflecting light, a first convex lens provided on the entrance surface side of the prism, and a second convex lens provided on the exit surface side of the prism. And a light redirecting device in which the light incident on the inside of the prism through the first convex lens is reflected on the reflecting surface and is emitted through the second convex lens.

[0023]

In the light redirecting device according to the first and second aspects of the present invention, the diffused light incident on the entrance surface of the prism is converged into substantially parallel light by the first convex lens and reflected by the reflecting surface. The light reflected by the reflection surface is guided to the emission surface,
The light is further converged by the second convex lens and emitted.

In this way, since the incident light is first focused into substantially parallel light by the first convex lens, all or most of the incident light can be guided to the second convex lens via the reflecting surface in the prism. Thereby, it becomes possible to secure a sufficient amount of light. In this case, it is sufficient for the first convex lens to reduce the incident light to such an extent that all or most of the incident light is guided to the second convex lens, and therefore it is not necessary to make the radius of curvature so small.

Further, since the light reflected by the reflecting surface is further focused by the second convex lens, a desired image forming distance and a desired beam spot diameter can be obtained. In this case, since the light incident on the second convex lens is narrowed down to some extent by the first convex lens, it is not necessary to increase the diameter of the second convex lens.

Therefore, it is possible to change the traveling direction of the light while realizing the desired converged light without disturbing the miniaturization and ensuring a sufficient light amount. In the photoelectric switch according to the third invention using the light redirecting device according to the first invention, the beam spot can be narrowed, so that good characteristics can be obtained.

[0027]

FIG. 1 is a view showing the structure of a prism lens according to an embodiment of the present invention, (a) is a front view, (b) is a side view, and (c) is a bottom view. This prism lens serves as a light redirecting device.

The prism lens 10 shown in FIG. 1 is made of a light conductor such as resin, has a first entrance / exit surface 11 that allows light to enter the inside or exits the outside, and has a front surface that allows the light to exit. It has a second entrance / exit surface 12 that exits or enters the inside, and has a reflecting surface 13 on the upper surface portion. First entrance / exit surface 11
And the second entrance / exit surface 12 form an angle of 90 ° with each other,
The reflecting surface 13 forms an angle of 45 ° with the first entrance / exit surface 11 and the second entrance / exit surface 12.

The first convex lens 1 is provided on the first entrance / exit surface 11.
4 is integrally formed, and a second convex lens 15 is integrally formed on the second entrance / exit surface 12. Further, the convex portions 16 for positioning are integrally formed on both side surfaces of the prism lens 10. The rear surface portion 17 of the prism lens 10 is formed to have an arc-shaped cross section.

On the reflecting surface 13 and the rear surface portion 17, a reflecting film made of aluminum or the like is vapor-deposited in order to increase the reflectance of light. The surface of the prism lens 10 is coated with silicon.

FIG. 2 is a vertical sectional view of the prism lens 10 shown in FIG. As shown in FIG. 2, the diffused light emitted from the tip of the optical fiber 40 enters the first entrance / exit surface 11 through the first convex lens 14. As a result, the diffused light is converged in parallel or to a degree close to it, and is bent at a substantially right angle by the reflecting surface 13. The reflected light is the second incident / emission surface 12
Is emitted from the second convex lens 15. As a result, the emitted light is further converged by the second convex lens 15.

In this way, the diffused light emitted from the tip of the optical fiber 40 is first narrowed down to some extent by the first convex lens 14, so that all or most of the incident light is passed through the reflecting surface 13 and the second convex lens 15. Can lead to. Thereby, a sufficient amount of light can be secured.
In this case, since it is sufficient for the first convex lens 14 to reduce the incident light to such an extent that all or most of the incident light is guided to the second convex lens 14, it is not necessary to make the radius of curvature so small.

Since the light reflected by the reflecting surface 13 is further focused by the second convex lens 15, a desired image forming distance and beam spot diameter can be obtained. in this case,
The light incident on the second convex lens 15 is reflected by the first convex lens 14
Since it is converged to some extent, it is not necessary to increase the diameter of the second convex lens 15 and it is not necessary to bring the tip of the optical fiber 40 into close contact with the first convex lens 14.

In this way, the traveling direction of the light emitted from the optical fiber 14 can be bent substantially at a right angle while realizing a desired converged light and securing a sufficient light amount. In this prism lens 10, the first convex lens 1
4. Since the second convex lens 15 and the convex portion 16 are integrally formed, the number of parts is reduced and the light transmission loss due to reflection on the surface is small. Further, the optical axis adjustment may be performed only between the prism lens 10 and the optical fiber 40.

According to the prism lens 10 of this embodiment, since the beam spot diameter of the emitted light can be narrowed at a fixed focal position, a sharp characteristic can be obtained especially when applied to a limited reflection type photoelectric switch. You can

FIG. 3 is an exploded perspective view of a projecting / receiving head of a limited reflection side-view type photoelectric switch using the prism lens of the above embodiment. The side-view type is capable of detecting the presence / absence of an object in a narrow detection position by bending light at a substantially right angle and projecting and receiving the light.

In FIG. 3, two prism lenses 10a, 10 are provided on a rectangular holding member 20 made of synthetic resin or the like.
Fixed frames 21a, 22 and 21b for fixing b are integrally formed. Fixed frames 21a and 21b are arranged on both sides of the fixed frame 22 with a predetermined space therebetween.

The prism lens 1 is provided inside the fixed frame 21a.
The concave portion 23 into which the one convex portion 16 (see FIG. 1) of 0a fits
a is formed, and a concave portion 24a into which the other convex portion 16 of the prism lens 10a is fitted is formed on one side portion of the fixed frame 22. Similarly, inside the fixed frame 21b, a concave portion 23b into which one convex portion 16 of the prism lens 10b fits is formed.
And a concave portion 24b into which the other convex portion 16 of the prism lens 10b is fitted is formed on the other side portion of the fixed frame 22.

The prism lens 10a has both convex portions 16
(Refer to FIG. 1).
The second convex lens 1
5 is positioned on the holding member 20 in a state where the member 5 faces diagonally forward. Similarly, in the prism lens 10b, both the convex portions 16 (see FIG. 1) are provided in the concave portions 23 of the fixing members 21b and 22.
The second convex lens 15 is positioned on the holding member 20 in a state in which the second convex lens 15 is directed obliquely forward by being fitted in b and 24b, respectively.

Recesses 25a and 25b are formed on the surface of the holding member 20 below the prism lenses 10a and 10b, respectively.
And the cylindrical optical fiber holding portions 26a and 26b are attached below the recesses 25a and 25b, respectively. The tips of the optical fibers 40a and 40b are inserted into the optical fiber holding portions 26a and 26b, respectively. As a result, the tips of the optical fibers 40a and 40b are positioned below the first convex lens 14 (see FIG. 1) of the prism lenses 10a and 10b, respectively. Further, holes 27 and 28 for screw insertion are formed in the holding member 20.

A lid member 30 is bonded and assembled to the holding member 20 by ultrasonic welding or the like. Like the holding member 20, the lid member 30 is also made of synthetic resin or the like. Window holes 31a and 31b are formed in the lid member 30 at positions corresponding to the second convex lenses 15 of the prism lenses 10a and 10b held by the holding member 20, respectively.

Further, the lid member 30 is provided with screw insertion holes 32 and 33 at positions corresponding to the screw insertion holes 27 and 28 of the holding member 20. When the lid member 30 is attached to the holding member 20, the convex lenses 15 of the prism lenses 10a and 10b are fitted into the window holes 31a and 31b, respectively.

FIG. 4 is a cross-sectional view of the light emitting / receiving head of FIG. As shown in FIG. 4, the prism lenses 10a and 10b
Of the first convex lens 14 with respect to the direction perpendicular to the front surface of the light projecting / receiving head so that the optical axes of the second convex lens 15 intersect each other at the detection position A separated by a distance L from the front surface of the light projecting / receiving head. It is tilted inward by an angle θ around the optical axis. Therefore, when using this light emitting and receiving head,
It is possible to detect whether or not the detection target object 50 exists at the detection position A that is separated by the distance L.

Since the convex portions 16 are formed on both side surfaces of each prism lens 10a, 10b and the rear surface portion 17 is chamfered in an arc shape, the thickness D of the light emitting / receiving head is kept thin at the designing or trial production stage. Second convex lens 1
The direction of the optical axis of 5 can be finely adjusted. That is,
Even if the angle θ of the optical axis of the second convex lens 15 is changed, the thickness D of the light emitting / receiving head does not have to be changed. Even when the thickness D of the light emitting / receiving head is the same, the first and second convex lenses 1
The size of 4, 15 can be increased. Therefore, the size of the light emitting / receiving head can be reduced.

FIG. 5 shows the holding member 20 and the prism lens 10
It is a front view showing the state where a and 10b were attached.
In FIG. 5, only the outline of the holding member 20 is drawn.

The light emitted from the tip of the optical fiber 40a enters the first convex lens 14 of the prism lens 10a and is reflected by the reflecting surface 13. The reflected light is shown in FIG.
As shown in, the light is emitted through the second convex lens 15 of the prism lens 10a and the window hole 31a. When the detection target object 50 exists at the detection position A which is separated from the light emitting / receiving head by a predetermined distance L, the emitted light is the detection target object 50.
The reflected light is reflected by the surface of the prism, passes through the window hole 31b, and enters the second convex lens 15 of the prism lens 10b. The incident light is reflected by the reflecting surface 13, is emitted from the first convex lens 14 of the prism lens 10b, and is guided to the tip of the optical fiber 40b, as shown in FIG.

When the light is emitted from the tip of the optical fiber 40b, the reflected light from the detection position A is guided to the tip of the optical fiber 40a by following the path opposite to the above. In this way, it is detected whether or not the detection target object 50 is present at the predetermined detection position A.

In the above embodiment, the prism lens 1
The convex portions 16 having a rectangular cross section are formed on both side surface portions of 0, 10a, and 10b, but the shape of the convex portions 16 is not limited thereto, and the convex portions 16 having a semicircular cross section or other shapes may be formed. . In addition, the prism lenses 10, 10a, 10
You may form two or more convex parts 16 in each side part of b. Further, in the above embodiment, the prism lenses 10, 10a,
Although the rear surface portion 10b of the prism lens 10b is chamfered to have an arc shape, the rear surface portion of the prism lenses 10, 10a and 10b may be chamfered into a polygonal shape.

The prism lenses 10 and 10 of the above embodiment
The a and 10b can also be applied to a lighting device that needs to bend light by 90 °.

[0050]

As described above, according to the first and second aspects of the invention, the first and second incident surfaces of the prism are respectively formed.
By providing the convex lens and the second convex lens of
While achieving the desired converged light and securing a sufficient amount of light,
It is possible to change the traveling direction of light. Further, according to the third invention, a photoelectric switch having good characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a front view, a side view, and a bottom view of a prism lens according to an embodiment of the present invention.

FIG. 2 is a vertical sectional view of the prism lens of FIG.

FIG. 3 is an exploded perspective view of a projecting / receiving head of a limited reflection side-view type photoelectric switch using the prism lens of FIG.

4 is a cross-sectional view of the light emitting / receiving head of FIG.

5 is a front view showing a state in which a prism lens is attached to a holding member of the light emitting / receiving head of FIG.

FIG. 6 is a diagram showing a conventional detection end structure of an optical fiber.

FIG. 7 is a diagram showing a conventional optical transmission device.

FIG. 8 is a diagram showing a conventional optical axis conversion device.

FIG. 9 is a diagram for explaining a cause of a problem in the conventional technique.

[Explanation of symbols]

 10a, 10b Prism lens 11 1st entrance / exit surface 12 2nd entrance / exit surface 13 Reflection surface 14 1st convex lens 15 2nd convex lens 16 Convex part 17 Rear surface part 40, 40a, 40b Optical fiber In each figure, The same reference numerals indicate the same or corresponding parts.

Claims (3)

[Claims] 1. A prism having an incident surface that guides light inside, an exit surface that emits light to the outside, and a reflecting surface that reflects light, a first convex lens provided on the incident surface side of the prism, and the prism. And a second convex lens provided on the exit surface side of the second convex lens, wherein the light incident on the inside of the prism through the first convex lens is reflected on the reflecting surface and is emitted through the second convex lens. Light redirecting device. 2. The first convex lens is a lens that converts light incident on the incident surface into substantially parallel light, and the second convex lens is a lens that converts light emitted from the exit surface into convergent light. The light redirecting device according to claim 1, wherein: 3. A photoelectric switch for detecting the presence or absence of the object by projecting the light onto the object and receiving the reflected light, the incident surface for guiding the light inside, the exit surface for emitting the light to the outside, and the light reflection A prism having a reflecting surface for controlling the incident angle, a first convex lens provided on the incident surface side of the prism, and a second convex lens provided on the exit surface side of the prism, and the prism passing through the first convex lens. A photoelectric switch characterized in that a light redirecting device is used, in which light incident inside is reflected on the reflection surface and emitted through the second convex lens.