KR101228761B1

KR101228761B1 - beam collector for Fabry-Perot interferometer and analysis system using the same

Info

Publication number: KR101228761B1
Application number: KR1020100137324A
Authority: KR
Inventors: 강명구; 야수아키 나가타; 박현철; 쇼헤이 하시구찌; 준 사사끼; 히로히사 야마다; 허형준; 임충수; 오기장
Original assignee: 니뽄스틸코포레이션; 주식회사 포스코
Priority date: 2010-12-28
Filing date: 2010-12-28
Publication date: 2013-01-31
Also published as: KR20120075261A

Abstract

The present invention relates to a beam collecting device for a Fabry-Perot interferometer and an analysis system using the same. Specifically, the beam collecting device for the Fabry-Perot interferometer of the present invention includes a measuring head for collecting a beam emitted from a target, the measuring head The beam shape deformation unit for transforming the shape of the beam transmitted in the annular shape, the light output unit for transmitting the beam modified in the beam shape deformation unit to the cavity, and the measuring head and beam shape deformation unit and the light output unit and beam shape deformation unit It includes an optical fiber for connecting.

Description

Beam collector for Fabry-Perot interferometer and analysis system using the same

The present invention relates to a beam collection device applied to a Fabry-Perot interferometer, a Fabry-Perot interferometer, and an analysis system using the beam collection device.

The conventional method for inspecting an object has become a main method of inspecting the state of the object by destroying or decomposing the object. However, the inspection method involving the above destruction is a suitable method when the object is a sampled one of a plurality of similar items, but is not suitable when the characteristics of the individual objects are unique or when the object is unique.

In recent years, non-destructive inspection methods have been proposed.

Among them, laser-ultrasound technology emits an ultrasonic wave to a measurement target and irradiates a pulsed laser to the measurement target to measure the reflected scattered laser using a laser interferometer. It has excellent field applicability. Therefore, it can be applied to the non-destructive inspection process, in particular on-line defect detection or material measurement.

However, in order to increase the accuracy of the inspection, it is necessary to improve the intensity of the laser light collected.

The present invention proposes a beam collection device that can improve the performance of the Fabry-Perot interferometer and a laser ultrasonic analysis system using the same.

The beam collecting device for a Fabry-Perot interferometer according to an embodiment of the present invention for solving the above problems is a measuring head for collecting the beam emitted from the target, the shape of the beam transmitted from the measuring head in a ring shape And a beam shape deformer, a light output part for transmitting the beam deformed by the beam shape deformer to the cavity, and an optical fiber connecting the measurement head and the beam shape deformer and the light output part and the beam shape deformer.

The beam shape deformer couples two optical fibers to deform the beam shape.

The beam shape deformer further includes a lens that focuses an output beam of the first optical fiber, and the beam focused by the lens is incident on the second optical fiber at a predetermined angle θ, and a focal length fc of the lens is provided. ), The circular beam is transformed into the annular beam by adjusting the distance d between the lens and the second optical fiber and the predetermined angle θ.

The beam collecting apparatus further includes a lens unit positioned between the light exiting unit and the cavity and converting the beam transmitted from the light exiting unit into parallel light.

An analysis system according to an embodiment of the present invention for solving the above problems is a laser irradiation device for irradiating a laser to a target, a beam collecting device for collecting the beam emitted from the target and transforming the shape of the beam to the cavity, A cavity for outputting a beam having a specific wavelength by resonating the beam transmitted from the beam collecting device, a converter for converting a beam output from the cavity into a digital electrical signal, and controlling the laser irradiation device, the cavity, and the converter; And a processor configured to signal-process the digital electrical signal converted by the converter to extract information about a target, wherein the beam collecting device collects a beam emitted from the target, and a beam of the beam transmitted from the measuring head. Beam shape deformer for deforming the shape into an annular shape, the beam deformed by the beam shape deformer to the cavity Output portion, and an optical fiber for connecting the measurement head and the beam shape deformations and output portion and the beam portion for transmitting deformation.

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According to the beam collecting device for the Fabry-Perot interferometer and the analysis system using the same of the present invention by the above solution, by transmitting the annular beam to the Fabry-Perot interferometer, it is possible to utilize a larger diameter optical fiber to improve the intensity of the transmitted light It can be increased while not degrading the interferometer efficiency.

In addition, according to the beam collecting device for the Fabry-Perot interferometer and the analysis system using the same of the present invention by the above solution, the laser-ultrasonic measurement efficiency is increased to improve the accuracy of the beam analysis, ultrasonic oscillation, measurement, signal analysis and modeling Can make great progress.

1 is a block diagram showing the configuration of the present invention and the conventional beam collecting device and Fabry-Perot interferometer.
2 is a structural diagram schematically showing the structure of the beam-form deformation part of the present invention.
3 is a diagram illustrating a configuration of an analysis system to which the beam collecting device of the present invention is applied.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, in describing in detail the operating principle of the preferred embodiment of the present invention, if it is determined that the detailed description of the related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

In order to clearly illustrate the present invention, parts not related to the description are omitted, and like parts are denoted by similar reference numerals throughout the specification.

In addition, when a part is said to "include" a certain component, this means that it may further include other components, except to exclude other components unless otherwise stated.

1 is a block diagram showing the configuration of the present invention and the conventional beam collecting device and Fabry-Perot interferometer.

Referring to FIG. 1, the beam transmitted to the cavity 200 by the beam collecting apparatus 100 of the present invention has an annular shape (a), and the beam transmitted to the cavity 200 by the conventional beam collecting apparatus. The shape of is circle (b).

Laser-ultrasound measurement efficiency is determined by the intensity of the signal light and the efficiency of the interferometer. However, in order to increase the field applicability of the recent measuring device, the signal light collected by the measuring head is transmitted to the interferometer and the analysis system using the optical fiber. And, in order to increase the signal-to-noise ratio (SNR), reception of more signal light is required at the measurement head. Therefore, application of an optical fiber with a large core diameter is necessary.

However, referring to FIG. 1, when the diameter of the optical fiber core for signal light transmission increases, the signal light incident on the interferometer in the conventional beam collecting device spreads in the vertical direction of the main axis of the interferometer. The light output after self-interference through multiple reflections in the cavity 200 of the Fabry-Parrot interferometer may have the same interference condition to simultaneously contribute to the measurement signal. Thus, multiple reflected lights should have the same optical path length (OPL).

However, OPL depends on the distance from the main axis of the interferometer. Therefore, in the case of a circular circle with a solid beam cross section, as in the conventional beam collecting device, the optical path lengths of the light at the center and the light near the circumference are different and thus cannot simultaneously contribute to the measurement signal.

In order to solve this problem, a method of narrowing a beam may be proposed. However, in order to realize this, there is a problem that the core width of the optical fiber must be reduced. Therefore, there is a need for a technology that uses a fiber with a large core but does not degrade the efficiency of the Fabri-Perot interferometer.

Accordingly, the beam collecting device of the present invention is incident on the interferometer with the shape of the optical fiber output light in an annular shape, so that the optical path lengths of the output light of the beam collecting device are all the same. Therefore, all the light output from the beam collecting device can contribute to the measurement signal at the same time.

In particular, in the case of output light of a multimode optical fiber having a large core diameter, an annular mode is included in the beam transmission mode. Therefore, a beam collecting device for outputting an annular beam by using two optical fibers for connecting the measuring head and the interferometer, and having a beam shape converting unit 120 for modifying the beam shape by adjusting the coupling conditions of the two optical fibers. Can be implemented.

Referring to FIG. 1, the beam collecting apparatus 100 of the present invention may include a measuring head 110, a beam shape converting unit 120, a light emitting unit 130, and optical fibers 141 and 143. It may be configured to further include a lens unit (150).

The measuring head 110 may collect the beam emitted from the target. In the non-destructive inspection and the like of the laser ultrasonic measurement method, since the phase change of the beam by the ultrasonic wave generated by irradiating the laser to the target is measured, a measuring head 110 for effectively collecting the beam emitted from the target is required.

The beam collected by the measuring head 110 may be transmitted to the beam shape deformation unit 120 through the optical fiber 141. The optical fibers 141 and 143 may include a core, which is a path along which the beam travels, and a cladding surrounding the core. In addition, the outer surface may be coated with synthetic resin once or twice to protect it from impact.

The total size excluding the protective coating is 100 to several hundred micrometers in diameter (1 μm = 1/1000 mm), and the refractive index of the core portion is higher than the refractive index of the cladding so that the light can be focused on the core portion and proceed without exiting well. It is.

Cores having a diameter of several micrometers are called single mode optical fibers, and those having tens of micrometers are called multimode optical fibers, and are divided into staircase and hill type optical fibers according to the refractive index distribution of the core.

The beam shape deformer 120 may deform the shape of the beam transmitted from the measuring head 110 into an annular shape. In particular, when the diameter of the core of the optical fiber increases, the beam transmitted through the fiber becomes circular and the optical path length of the beam is different according to the position of the inside of the circular beam. It is possible to ensure that the optical path lengths between them match within a certain range.

The beam shape deformation unit 120 may couple the two optical fibers 141 and 143 to form an annular beam. In particular, the beam shape deformation unit 130 may form an annular beam by coupling the cores of the two optical fibers 141 and 143 to be spaced apart from each other.

The beam whose shape is modified in the beam shape deformation unit 120 may be transmitted to the light exit unit 130 through the optical fiber 143.

The light exit unit 130 may transmit the beam whose shape is modified by the beam shape deformation unit 120 to the cavity 200. The light exit unit 130 may be formed by simply terminating the optical fiber 143 to a predetermined size, or may be formed by attaching a port.

The lens unit 150 may convert the beam output from the light exit unit into parallel light and transmit the converted beam to the cavity 200.

2 is a structural diagram schematically showing the structure of the beam-form deformation part of the present invention.

Referring to FIG. 2, the beam shape deforming unit 120 of the present invention may make the annular beam by inclining the optical fibers 141 and 143 to be spaced apart from each other.

The port 121 may be connected to the end of the optical fiber 141 on the measurement head 110 side, and the port 125 may be connected to the end of the optical fiber 143 on the light exiting unit 130 side.

The circular beam output from the optical fiber 141 on the measurement head 110 side is collected at one point by the lens 123 and is incident on the optical fiber 143 on the light exiting unit 130 side. .

The beam shape modifying unit 120 adjusts the focal length fc of the lens 123, the distance d between the lens and the optical fiber 143 on the light exiting side 130, and the incident angle θ to adjust the circular beam. It can be transformed into an annular beam at.

3 is a diagram illustrating a configuration of an analysis system to which the beam collecting device of the present invention is applied.

Referring to FIG. 3, the beam output from the beam collecting device passes through the path setting device 400 and is incident to the cavity 200.

Although not shown, the analysis system of the present invention includes a laser irradiation device for irradiating a laser for a non-destructive inspection on a target and a beam collecting device for collecting a laser beam emitted from the target.

The path setting device 400 may transfer the beam transmitted from the beam collecting device to the cavity 200 and the beam output from the cavity 200 to the analysis device 300.

The cavity 200 may reflect the beam transmitted from the path setting device 400 at the incident surface or may resonate and transmit the transmitted beam therein.

The beam reflected from the incident surface is a reflection beam (R), and the beam transmitted and resonated inside the cavity 200 is called a transmission beam (T).

The converter 330 may convert the output beams R and T into digital electric signals in the cavity 200.

In addition, if necessary, the analysis system may further include an amplifier 310 and a signal shutter 320.

The amplifier 310 may amplify the intensity of the reflected beam (R) and the transmission beam (T) to make an intensity suitable for conversion into an electrical signal for beam analysis.

The signal shutter 320 may detect the input optical signal at each preset timing. This is similar to the sampling technique used for signals in radio bands with frequencies lower than light.

The processor 340 may process information about a target by signal processing the digital electrical signal generated by the converter 330, and may control operations of the laser irradiation apparatus, the cavity, and the converter.

The analysis system using the beam collection device of the present invention can collect the beam irradiated to the target and efficiently transmit it to the cavity 200 can improve the analysis performance of the analysis system.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and it is common in the art that various substitutions, modifications, and changes can be made without departing from the technical spirit of the present invention. It will be apparent to those skilled in the art.

100: beam collecting device 200: cavity
110: measuring head 120: beam shape deformation portion
130; Light exiting section 141, 143: optical fiber
150:
300: analysis device
310: amplification unit 320: signal shutter
330: converter 340: processor
400: routing device

Claims

A measuring head collecting the beam emitted from the target;
A beam shape modifying unit which deforms the shape of the beam transmitted from the measuring head into an annular shape;
A light output unit configured to transfer the beam deformed by the beam shape deformer to a cavity;
A first optical fiber connecting the measurement head and the beam shape deformation unit; And
And a second optical fiber connecting the light exiting part and the beam shape deforming part.

The method of claim 1, wherein the beam shape deformation portion
A beam collection device for a Fabry-Perot interferometer coupling the first and second optical fibers to modify the beam shape.

The method of claim 2, wherein the beam shape deformation unit further comprises a lens for focusing the output beam of the first optical fiber,
The beam focused by the lens is incident on the second optical fiber at a predetermined angle θ,
Beam for Fabry-Perot interferometer that transforms the circular beam into the annular beam by adjusting the focal length fc of the lens, the distance d between the lens and the second optical fiber, and the predetermined angle θ. Collection device.

The method of claim 1, wherein the beam collecting device
And a lens unit positioned between the light exiting unit and the cavity and converting the beam transmitted from the light exiting unit into parallel light.

A laser irradiation device for irradiating a laser onto a target;
A beam collecting device which collects the beam emitted from the target and transmits the beam to the cavity by modifying the shape of the beam;
A cavity for resonating the beam transmitted from the beam collecting device and outputting a beam having a specific wavelength;
A converter for converting the beam output from the cavity into a digital electric signal; And
And a processor for controlling the laser irradiation device, the cavity and the converter, and extracting information on a target by processing a digital electrical signal converted by the converter.
The beam collecting device
A measuring head collecting a beam emitted from the target;
A beam shape modifying unit which deforms the shape of the beam transmitted from the measuring head into an annular shape;
An output unit configured to transmit light to the cavity from the beam deformed by the beam shape deformer; And
And an optical fiber connecting the measuring head to the beam shape deformation part and the light exiting part and the beam shape deformation part.

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