JP2002257726A - Photoelectric sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a small detection object to be detected and determined. SOLUTION: An beam emitted from a light source is allowed to get incident into an optical fiber 14 of a small diameter compared with a conventional one, since lights of two wavelengths are emitted from the substantially same position by using as the light source a semiconductor laser element (LD10) emitting the laser beam having the two wavelengths from one element. A light spot projected to the small detection object 30 is made small thereby to detect and determine even the small detection object.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a photoelectric sensor using light of a plurality of wavelengths.

[0002]

2. Description of the Related Art Some photoelectric sensors detect an object to be detected by using light of two or more wavelengths, or determine the front and back of the object to be detected and the color. There is. As a configuration of such a photoelectric sensor, two light sources having different wavelengths, for example, light emitting diodes (hereinafter, referred to as LEDs) are provided, and light emitted from these light sources is made identical by using an optical system such as a half mirror or a beam splitter. In some cases, the light is incident on an optical fiber for light emission along the optical axis and is emitted toward the detection target. However, the photoelectric sensor having such a configuration has a disadvantage that the number of components is increased by the provision of the two light sources, which leads to an increase in the size of the device.

On the other hand, there is a light source that emits light of a plurality of wavelengths with one light source, specifically, a photoelectric sensor using a two-wavelength LED. The two-wavelength LED has two types of LED chips arranged in one element package, and can be handled as one light emitting element, so that the device can be downsized.

[0004]

However, in recent years,
The object to be detected by the photoelectric sensor has also been extremely miniaturized, for example, like a chip-type electronic component. In order to accurately detect and discriminate a smaller detection target, it is necessary to reduce the size of the light spot projected on the detection target. Therefore, it is required to make the diameter of the optical fiber smaller.

However, when light from the two-wavelength LED is passed through a small-diameter optical fiber, the following problem occurs. That is, as described above, the two-wavelength LED includes two LED chips in one element package.
Since two elements are arranged in one package, 2
The positions where two lights are emitted are separated. The diameter of the optical fiber must be such that the incident angle of light from each LED chip does not exceed the maximum incident angle (numerical aperture) of the optical fiber. Had become. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a photoelectric sensor capable of detecting and determining even a smaller detection target.

[0006]

According to a first aspect of the present invention, there is provided a photoelectric sensor which emits a plurality of wavelengths of laser light from one element, and a semiconductor laser element which is connected to one end of the semiconductor laser element. A light emitting optical fiber that receives light emitted from the laser element and transmits the light to the other end, and receives light emitted from the light emitting optical fiber from one end and transmits the light to the other end. It is characterized in that it comprises a light receiving optical fiber and light receiving means for receiving light transmitted from the light receiving optical fiber.

[0007]

According to the first aspect of the present invention, by using a semiconductor laser device that emits laser light of a plurality of wavelengths from one device as a light source, light of a plurality of wavelengths is emitted from substantially the same position. Therefore, light emitted from the light source can be made incident on an optical fiber having a smaller diameter than in the related art. This makes it possible to reduce the size of the light spot projected on the detection target, and to detect and determine even a smaller detection target.

[0008]

Next, an embodiment of the present invention will be described with reference to FIGS. The photoelectric sensor according to the present embodiment performs, for example, detection of an object to be detected, front / back discrimination, or discrimination of a color, and FIG. In the figure, reference numeral 10 denotes a semiconductor laser device (hereinafter, referred to as LD). The LD 10 emits laser beams of two different wavelengths from one element, and has a well-known configuration. Although not shown in detail, one element is provided with two active layers having different compositions. When a current flows through the layer, light of two different wavelengths is oscillated while being alternately switched at high speed.

The light emitted from the LD 10 is collimated by a collimator lens 11 and then converged to a multi-core fiber 13 via a converging lens 12. Multi-core fiber 13
Is an optical fiber 14 having a large diameter at the center as shown in FIG.
(Corresponding to the “light-projecting optical fiber” of the present invention), and a number of thin optical fibers 15 (corresponding to the “light-receiving optical fiber” of the present invention) are annularly arranged on the outer periphery to protect the outermost periphery. It has a structure covered with a jacket 16. At one end of the multi-core fiber 13, a part of the protective jacket 16 is cut off, and a plurality of optical fibers 15 exposed therefrom are bundled together and branched from the optical fiber 14. Said L
The light emitted from D10 passes through the lenses 11 and 12, and enters from the branch end of the optical fiber 14 (the collimator lens 11 and the like are not shown in FIG. 2). The light that has entered the optical fiber 14 exits from the other end, passes through the converging lens 18, and irradiates the irradiation surface 31 or the detection target 30 that passes over the irradiation surface 31.
It is projected on.

The reflected light from the irradiation surface 31 or the detection object 30 passes through the converging lens 18 again, enters from one end of each optical fiber 15, and is transmitted to the other side. The light emitted from the end of the optical fiber 15 on the branch side passes through the converging lens 19 and is received by the light receiving element 21 (corresponding to "light receiving means" of the present invention). When receiving light, the light receiving element 21 outputs a light receiving signal to a detection circuit (not shown). The detection circuit obtains a reflectance ratio for the light of two wavelengths based on the light receiving signal from the light receiving element 21, and performs processing such as detection of the detection target 30, discrimination of the front and back or color discrimination from the change in the ratio. I do.

According to this embodiment, a semiconductor laser device (LD1) that emits laser beams of two wavelengths from one device
By using 0) as the light source, light of two wavelengths is emitted from substantially the same position, so that the light emitted from the light source can be made incident on the optical fiber 14 having a smaller diameter than in the related art. This makes it possible to reduce the size of the light spot projected on the detection target 30 and detect and determine even a smaller detection target. Further, as compared with the conventional case where two light sources having different wavelengths are provided, the number of light sources is reduced, and no optical system components such as a beam splitter are required, so that the number of components is reduced and the cost is reduced. be able to. Further, since no strict alignment adjustment is required when aligning the optical axes of the two light sources, the operation cost can be reduced.

The technical scope of the present invention is not limited by the above-described embodiment. For example, the followings are also included in the technical scope of the present invention. (1) In the above embodiment, the optical fiber 14 at the center of the multi-core fiber 13 is used for projecting light, and the thin optical fiber 15 is used for receiving light. However, these may be reversed. The two optical fibers for projecting and receiving light may be separately configured one by one, or may be coupled via an optical coupling means such as a fiber coupler. Also, as shown in FIG.
One optical fiber may also be used for light emission and light reception. In this photoelectric sensor, two-wavelength laser light emitted from the semiconductor laser element 40 is converted into parallel light by a collimator lens 41 and passes through a half mirror 42. Then, the light enters the one end of the optical fiber 44 through the converging lens 43, is emitted from the other end, and is emitted to the detection object 46 through the converging lens 45. The reflected light from the detection object 46 passes through the converging lens 45 again and is incident on one end of the optical fiber 44, and the light emitted from the other end is reflected by the half mirror 42 after passing through the converging lens 43, The light is received by the light receiving element 47.

(2) In the above embodiment, the reflection type photoelectric sensor for receiving the light reflected from the object to be detected has been described.
The present invention can be applied to a transmission type photoelectric sensor as shown in FIG. 4, for example. In this photoelectric sensor, the light emitted from the semiconductor laser element 50 is emitted to the detection target 52 through the light emitting optical fiber 51. The detection target 52 is a light transmitting body such as a glass wafer or an LCD glass,
The light transmitted through the detection target 52 passes through the light receiving optical fiber 53 and is received by the light receiving means 54. Even in such a transmission type photoelectric sensor, a smaller detection target can be detected and determined by reducing the diameter of the optical fiber. (3) In the above embodiment, the configuration is such that an optical lens such as a collimator lens or a converging lens is provided. However, a configuration without an optical lens may be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a photoelectric sensor according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a multi-core fiber.

FIG. 3 is a configuration diagram of a photoelectric sensor according to another embodiment.

FIG. 4 is a configuration diagram of a photoelectric sensor according to another embodiment.

[Explanation of symbols]

10, 40, 50: semiconductor laser element 14: optical fiber (light emitting optical fiber) 15: optical fiber (light receiving optical fiber) 21, 47, 54: light receiving element (light receiving means) 44: optical fiber (light emitting) (Optical fiber, optical fiber for light reception) 51 ... optical fiber for light projection 53 ... optical fiber for light reception

Claims (1)

[The claims] 1. A semiconductor laser device that emits laser beams of a plurality of wavelengths from one device, a light projecting optical fiber that receives light emitted from the semiconductor laser device from one end and transmits the light to the other end. A light-receiving optical fiber that receives light emitted from the light-projecting optical fiber from one end and transmits the light to the other end; and a light-receiving unit that receives light transmitted from the light-receiving optical fiber. A photoelectric sensor, comprising: