JPH0625809U - Optical fiber type photoelectric switch - Google Patents

Abstract

(57) [Abstract] [Purpose] To improve the coupling efficiency between a light emitting element and an optical fiber and / or a light receiving element and an optical fiber, and to improve the sensitivity of a photoelectric switch. [Structure] A cone type optical device 5 is installed between a light emitting element 1 and an optical fiber 3. The cone-shaped optical device 5 is formed by surrounding the outer circumference of a truncated cone-shaped core 5a with a clad 5b, and has a large-diameter light inlet / outlet 10 and a small-diameter light inlet / outlet 11 at both ends. The large-diameter light inlet / outlet 10 is optically coupled to the front surface of the light emitting element 1, and the small-diameter light inlet / outlet 11 is optically coupled to the end surface of the optical fiber 3. When the light emitting chip 1a of the light emitting element 1 is caused to emit light, the light spreads at a predetermined directivity angle, and the light of the maximum directivity angle is also incident on the large-diameter light entrance / exit 10 of the optical device 5 from the front surface of the light emitting element 1 and is small. Most of the light is guided to the light inlet / outlet 11 having a diameter and enters the optical fiber 3.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an optical fiber type photoelectric switch that detects the presence or absence of an object in a predetermined detection space by using an optical fiber.

[0002]

[Prior art]

 A photoelectric switch that detects the presence or absence of an object in a predetermined detection space uses a flexible optical fiber, and is widely used because it can be applied to a narrow detection space and is excellent in versatility. A conventional example of this optical fiber type photoelectric switch is shown in FIG. 4 and will be described.

FIG. 4 shows an optical system portion of a photoelectric switch. That is, a pair of a light emitting element 1 and a light receiving element 2, a light projecting optical fiber 3 and a light receiving optical fiber 4 each of which has one end optically coupled. The light emitting element 1 is an infrared light emitting LED or the like, and contains a light emitting chip 1a. The light receiving element 2 is a phototransistor or the like and has a light receiving chip 2a built therein. The light emitting element 1 and the light receiving element 2 are connected to an amplifier circuit (not shown) that controls the light emitting signal and the light receiving signal.

As shown in FIG. 5, the light emitting chip 1a of the light emitting element 1 is installed in the recess 1c of the reflecting plate 1b which also serves as an electrode. When the light emitting chip 1a is made to emit light by energization, the light is reflected on the inner surface of the concave portion 1c, transmitted through the front surface of the light emitting element 1, and enters the optical fiber 3.

The optical fiber 3 is a glass fiber or a plastic fiber in which a core 3a having a large refractive index is surrounded by a clad 3b having a small refractive index. One end surface of the optical fiber 3 is butted and coupled to the front surface of the light emitting element 1. The other end of the optical fiber 3 is arranged in the detection space 7. The light that has entered the one end of the optical fiber 3 from the light emitting element 1 passes through the core 3a of the optical fiber 3 and is projected into the detection space 7 from the other end.

The light receiving element 2 and its optical fiber 4 have the same structure as the light emitting element 1 and its optical fiber 3. The front ends of the light projecting optical fiber 3 and the light receiving optical fiber 4 are arranged opposite to each other on both sides of the detection space 7 with their optical axes aligned with each other.

When there is no object in the detection space 7, light enters the light receiving optical fiber 4 from the light projecting optical fiber 3, passes through the optical fiber 4, and is received by the light receiving chip 2 a of the light receiving element 2. Then, the light receiving chip 2a outputs an electric signal. If there is an object in the detection space 7 and this object blocks the light of the light projecting optical fiber 3, the light does not enter the light receiving optical fiber 4 and the light receiving element 2a does not operate.

Although the illustrated example is of a transmission type, the reflection type photoelectric switch that irradiates the detection position from the light projecting optical fiber 3 and receives the reflected light by the light receiving optical fiber 4 has the same principle. is there.

[0009]

[Problems to be solved by the device]

 The light-emitting element 1 has a small diameter of about several mm, and the optical fiber 3 has a diameter of about 0.5 mm, which has been further reduced in size to improve quality and expand applications. The same applies to the light receiving element 2. However, the coupling efficiency between the light emitting element 1 and its optical fiber 3 is poor, and similarly, the coupling efficiency between the light receiving element 2 and its optical fiber 4 is poor, causing the problems described below.

That is, as shown in FIG. 5, the light projected from the light emitting element 1 spreads with a certain directional angle, and only the light in the vicinity of the optical axis of the light emitting element 1 enters the narrow optical fiber 3. , Other light is wasted. Therefore, the light from the light emitting chip 1a is reflected by the concave portion 1c of the reflection plate 1b to make the directivity angle of the light from the light emitting element 1 smaller so that more light is incident on the optical fiber 3. However, there is still a lot of wasted light.

Further, although the light emitting element 1 and the optical fiber 3 are coupled with their optical axes aligned with each other, the optical axes between the two may be misaligned during or after the coupling. The deviation of the optical axis reduces the amount of light incident from the light emitting element 1 to the optical fiber 3 and increases light waste.

Similarly, the light incident on the light receiving element 2 from the light receiving optical fiber 4 also spreads at a predetermined directivity angle, and a part of the light is only received by the light receiving element 2a, so much light is wasted. As it is.

Such light waste deteriorates the coupling efficiency of the light emitting element 1 and the optical fiber 3, and the light receiving element 2 and the optical fiber 4, and deteriorates the sensitivity of the photoelectric switch.

The effective maximum length of the pair of optical fibers 3 and 4 is determined within a range in which the optical attenuation factor of the pair of optical fibers 3 and 4 can be calculated and the function as a photoelectric switch can be exerted. However, since the coupling efficiency between the light emitting element 1 and the optical fiber 3 is poor and the absolute value of the amount of light incident on the optical fiber 3 is low, in the case of the optical fiber 3 having a wire diameter of about 0.5 mm, its effective maximum value is obtained. The length was up to several tens of cm, and it was difficult to make it longer than that. As a result, the maximum distance between the light emitting element 1 and the light receiving element 2 and the detection space 7 is limited to several tens of cm, which makes it difficult to expand the environment in which the photoelectric switch can be used.

An object of the present invention is to provide a photoelectric switch having high sensitivity and capable of increasing the length of an optical fiber by increasing the coupling efficiency between the light emitting element and / or the light receiving element and the optical fiber. .

[0016]

[Means for Solving the Problems]

 The present invention achieves the above-mentioned object by optically coupling a light emitting element and / or a light receiving element and an optical fiber with a cone type optical device having an optical axis aligned between them.

[0017]

[Function] A cone-type optical device is a short optical fiber with a clad on the outer circumference of a truncated cone core. It has a large-diameter light inlet and outlet and a small-diameter light inlet and outlet at both ends. The light incident on the entrance is condensed and projected from the light entrance / exit with a small diameter, and conversely, the light incident on the light entrance / exit with a small diameter is projected from the light entrance / exit with a large diameter with the directivity angle regulated.

Therefore, when the cone-shaped optical device is installed with its large-diameter light inlet / outlet facing the light emitting element and its small-diameter light inlet / outlet facing the end face of the optical fiber, the light from the light emitting element is collected by the cone-shaped optical device. Since the light is incident on the optical fiber, the cone type optical device reduces light waste and improves the coupling efficiency between the light emitting element and the optical fiber. If a cone-shaped optical device is installed with its large-diameter light inlet / outlet facing the light-receiving element and its small-diameter light inlet / outlet directed toward the end face of the optical fiber, the conventional light beam from the optical fiber has a large directivity angle and is not wasted. The conical optics collects the incident light toward the light-receiving element and makes it incident. The cone-type optics reduces the light waste and improves the coupling efficiency between the light-receiving element and the optical fiber.

Further, due to the improvement of the coupling efficiency by the cone type optical device, the amount of light incident on the optical fiber increases, the sensitivity of the photoelectric switch increases correspondingly, and the effective maximum length of the optical fiber can be increased.

[0020]

【Example】

 The embodiment shown in FIGS. 1 to 3 will be described. 4 and 5 of the embodiment shown in FIG. 5 are designated by the same reference numerals, and different points will be described.

In the embodiment shown in FIG. 1, a cone type optical device 5 is arranged between the light emitting element 1 and the optical fiber 3 with their optical axes aligned, and a cone type optical device is arranged between the light receiving element 2 and the optical fiber 4. It is characterized in that the container 6 is arranged with its optical axis aligned.

As shown in FIG. 2, the projection-side cone-shaped optical device 5 has a structure in which the outer periphery of a truncated cone-shaped core 5a is surrounded by a clad 5b, which is a short optical fiber (not shown). Is manufactured by compressing into a truncated cone shape. The optical device 5 has a large-diameter light entrance / exit 10 and a small-diameter light entrance / exit 11 at both ends. The large-diameter light inlet / outlet 10 is optically coupled to the front surface of the light-emitting element 1, the small-diameter light inlet / outlet 11 is optically coupled to the end surface of the optical fiber 3, and the cone-shaped optical device 5 optically couples the light-emitting element 1 and the optical fiber 3 to each other. Join.

The diameter of the core 5 a at the large-diameter light entrance / exit 10 of the optical device 5 is substantially equal to the diameter of the light projection opening on the front surface of the light emitting element 1. The diameter of the core 5a at the small-diameter light entrance / exit 11 of the optical device 5 is substantially the same as the diameter of the core 3a at one end of the optical fiber 3.

Therefore, when the light emitting chip 1 a of the light emitting element 1 is made to emit light, the light is spread at a predetermined pointing angle, and the light with the maximum directivity angle is also emitted from the front surface of the light emitting element 1 to the large-diameter light entrance / exit of the optical device 5. Incident on 10. The light that has entered the core 5a of the optical device 5 is reflected by the cladding 5b, is condensed, is guided to the small-diameter light entrance / exit 11, and most of it enters the core 3a of the optical fiber 3.

In other words, the optical device 5 guides most of the light from the light emitting element 1 to the optical fiber 3 and almost eliminates the waste of light leaking to the outside, thereby increasing the coupling efficiency between the light emitting element 1 and the optical fiber 3. By increasing the amount of light incident on the optical fiber 3, the effective maximum length of the optical fiber 3 can be increased within a range where the function as a photoelectric switch is exhibited. For example, in the case of the optical fiber 3 having a wire diameter of 0.5 mm, it is known that its effective maximum length exceeds 1 m.

FIG. 3 shows a practical structure and a mounting structure of the optical device 5. For example, the optical device 5 has a structure having parallel portions 5d and 5e on both sides of a central portion 5c having a truncated cone shape, and is housed and held in a cylindrical base 8. By connecting the base 8 to the light emitting element 1 and the optical fiber 3, the optical device 5 is fixedly arranged between the light emitting element 1 and the optical fiber 3 with their optical axes aligned.

The cone-shaped optical device 6 on the light receiving side has a size and structure that guides the light projected from the tip of the optical fiber 4 to the light receiving chip 2 a of the light receiving element 2 without waste. This optical device 6 also has a structure in which the outer circumference of a truncated cone-shaped core 6a is surrounded by a clad 6b, and has a small-diameter light entrance / exit 12 and a large-diameter light entrance / exit 13 at both ends. The small-diameter light inlet / outlet 12 is optically coupled to the end surface of the optical fiber 4, and the large-diameter light inlet / outlet 13 is optically coupled to the front surface of the light receiving element 2.

The light-receiving side optical device 6 guides the light of the optical fiber 4 to the light-receiving element 2 without waste by the principle opposite to that of the light-projecting side optical device 5, and increases the coupling efficiency between the optical fiber 4 and the light-receiving element 2. Therefore, the effective maximum length of the light-receiving side optical fiber 4 can be increased.

In the above embodiment, the cone type optical device is installed on both the light emitting element and the light receiving element. However, the present invention is not limited to this example, and depending on the type and application of the photoelectric switch, only on the light emitting element side or the light receiving element side. The cone type optical device may be arranged only on the element side.

[0030]

[Effect of device]

 According to the present invention, the addition of the cone type optical device further improves the coupling efficiency between the light emitting element and the optical fiber and the coupling efficiency between the light receiving element and the optical fiber, and thus the sensitivity of the photoelectric switch can be easily improved. .

Further, the amount of light incident on the optical fiber is increased by the addition of the cone type optical device, and the effective maximum length of the optical fiber within the range where the function of the photoelectric switch is exerted can be increased by that much, and more It also has the effect of providing a versatile photoelectric switch that can be applied to the environment.

[Brief description of drawings]

FIG. 1 is a side view of an essential part including a partial cross section of a photoelectric switch showing an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view showing an optical coupling structure on a light projecting side of a photoelectric switch.

FIG. 3 is a side view including a partial cross section showing a practical structure of a light projecting side of the photoelectric switch in FIG.

FIG. 4 is a side view of a main part of a conventional photoelectric switch.

FIG. 5 is an enlarged cross-sectional view showing an optical coupling structure on the light projecting side of the photoelectric switch.

[Explanation of symbols]

 1 Light emitting element 2 Light receiving element 3 Optical fiber 4 Optical fiber 5 Cone type optical device 6 Cone type optical device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Setsuo Makino 2-11-12 Sonezaki, Kita-ku, Osaka-shi, Osaka Prefecture Hokuyo Electric Co., Ltd. (72) Toshihiro Mori 2-chome Sonezaki, Kita-ku, Osaka-shi, Osaka No. 12 inside Hokuyo Electric Co., Ltd.

Claims (1)

[Scope of utility model registration request] 1. A photoelectric switch in which a light emitting element and a light receiving element are optically coupled by an optical fiber, wherein at least one of the light emitting element and the light receiving element and an optical fiber are arranged in a cone shape with their optical axes aligned with each other. An optical fiber type photoelectric switch characterized by being optically coupled by an optical device.