KR19990020915A - Displacement measuring device and displacement measuring method using same - Google Patents
Displacement measuring device and displacement measuring method using same Download PDFInfo
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- KR19990020915A KR19990020915A KR1019970044392A KR19970044392A KR19990020915A KR 19990020915 A KR19990020915 A KR 19990020915A KR 1019970044392 A KR1019970044392 A KR 1019970044392A KR 19970044392 A KR19970044392 A KR 19970044392A KR 19990020915 A KR19990020915 A KR 19990020915A
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- light
- diffraction grating
- diffraction
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- 238000006073 displacement reaction Methods 0.000 title claims abstract description 47
- 238000000034 method Methods 0.000 title description 6
- 238000006243 chemical reaction Methods 0.000 claims description 7
- 230000002452 interceptive effect Effects 0.000 claims description 2
- 230000003287 optical effect Effects 0.000 abstract description 9
- 238000005259 measurement Methods 0.000 abstract description 6
- 238000010586 diagram Methods 0.000 description 2
- 230000010287 polarization Effects 0.000 description 2
- 230000000737 periodic effect Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/16—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge
- G01B11/165—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge by means of a grating deformed by the object
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
- G01B11/2441—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures using interferometry
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/30—Measuring arrangements characterised by the use of optical techniques for measuring roughness or irregularity of surfaces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/36—Forming the light into pulses
- G01D5/38—Forming the light into pulses by diffraction gratings
Abstract
본 발명은 광원과, 상기 광원의 하부에 상기 광원으로부터 나온 광이 입사하는 제1 회절격자와, 상기 제1 회절격자를 통과한 광은 브래그 조건에 맞는 일정한 회절각을 갖는 ±m차 회절광으로 변경되며 상기 ±m차 회절광이 입사하도록 상기 제1 회절격자의 하부에 상기 제1 회절격자에 수직하게 위치하는 두 개의 거울과, 상기 거울의 하부에 상기 거울에 반사된 ±m차 회절광이 상기 회절각과 동일한 각도로 입사되고 상기 제1 회절격자와 간격이 같은 제2 회절격자와, 상기 제2 회절격자를 통과한 ±m차 회절광은 상기 제2 회절격자에 수직하게 회절되어 ±m'차 회절광으로 변경되며 상기 제2 회절격자의 하부에 상기 ±m'차 회절광의 위상차이로 인한 간섭광의 발생 및 세기 변화를 측정하는 광전센서를 포함하여 이루어진다. 본 발명의 변위측정장치는 광학계의 구성요소가 간편하며, 광축 정렬이 용이하다. 또한, 본 발명의 변위측정장치는 2개의 회절격자를 이용하여 변위를 측정하기 때문에 가공 및 측정기기의 측정 분해능 및 정밀도를 높일 수 있다.The present invention provides a light source, a first diffraction grating in which light from the light source is incident to the lower part of the light source, and light passing through the first diffraction grating is ± m-d order diffraction light having a constant diffraction angle suitable for Bragg conditions. Two mirrors positioned at a lower portion of the first diffraction grating perpendicularly to the first diffraction grating so that the ± m diffraction diffracted light is incident, and a ± m-d order diffracted light reflected by the mirror at the lower part of the mirror A second diffraction grating incident at the same angle as the diffraction angle and spaced apart from the first diffraction grating, and the ± m-d order diffracted light passing through the second diffraction grating is diffracted perpendicularly to the second diffraction grating and ± m ' And a photoelectric sensor which is changed to the differential diffracted light and measures the generation and intensity change of the interference light due to the phase difference of the ± m 'diffraction diffraction light under the second diffraction grating. Displacement measuring device of the present invention is a simple component of the optical system, the optical axis alignment is easy. In addition, since the displacement measuring device of the present invention measures the displacement using two diffraction gratings, it is possible to increase the measurement resolution and precision of the processing and measuring equipment.
Description
본 발명은 변위측정장치 및 이를 이용한 변위측정방법에 관한 것으로, 특히 두 개의 회절격자를 이용하여 변위를 측정하는 변위측정장치 및 그 방법에 관한 것이다.The present invention relates to a displacement measuring apparatus and a displacement measuring method using the same, and more particularly, to a displacement measuring apparatus and a method for measuring displacement using two diffraction gratings.
일반적으로, 변위측정장치는 가공 및 측정기기의 직선 또는 각도 변위를 측정하는 장치이다. 특히, 가공 및 측정기기의 변위 측정은 생산제품의 신뢰성 등에 매우 큰 영향을 미치므로 측정분해능 및 정밀도가 높아야 한다. 여기서, 종래의 변위측정장치를 설명한다.In general, the displacement measuring device is a device for measuring the linear or angular displacement of the processing and measuring equipment. In particular, the displacement measurement of processing and measuring equipment has a great influence on the reliability of the produced product, so the measurement resolution and precision should be high. Here, a conventional displacement measuring apparatus will be described.
도 1은 종래의 변위측정장치를 개략적으로 도시한 도면이다.1 is a view schematically showing a conventional displacement measuring device.
구체적으로, 입사하는 광은 하브 미러(11)를 이용하여 광 a 과 광 b로 분리된다. 상기 광 a 및 광 b는 각각 두 개의 거울(13, 15)을 이용하여 회절 격자(17)에 입사되고 회절되어 회절광 a' 및 b'을 발생시킨다. 이때, 광 b는 λ/4 파장플레이트(waveplate : 16)를 통과하여 광 b의 위상을 90도 지연시킨다. 이렇게 회절된 회절광 a' 및 b'은 합쳐져 간섭광이 만들어지며, 상기 회절광 a'와 b'간은 위상차 90도를 갖게 되며 상기 회절격자(17)의 변위에 따라 명암변화가 발생한다. 따라서, 이러한 합쳐진 회절광 a' 및 b'의 명암변화를 측정하여 회절격자의 변위를 측정한다. 상기 간섭광의 명암 변화의 측정은 먼저 상기 간섭광을 거울(19)을 통하여 편광 빔 스플리터(21)에 입사시켜 상기 간섭광을 두 개의 편광 성분으로 분해한 후, 이를 각각 광검출기(23, 25)에 의하여 검출함으로써 수행한다.Specifically, the incident light is separated into light a and light b using the harve mirror 11. The light a and light b are respectively incident on the diffraction grating 17 and diffracted using two mirrors 13 and 15 to generate diffracted light a 'and b'. At this time, the light b passes through the λ / 4 waveplate 16 to delay the phase of the light b by 90 degrees. The diffracted light beams a 'and b' thus diffracted are combined to produce interference light. The diffracted light beams a 'and b' have a phase difference of 90 degrees and a change in contrast occurs according to the displacement of the diffraction grating 17. Therefore, the change of the contrast of the combined diffracted light a 'and b' is measured to measure the displacement of the diffraction grating. The measurement of the change in the intensity of the interference light is first introduced into the polarization beam splitter 21 through the mirror 19 to decompose the interference light into two polarization components, and then the photodetectors 23 and 25 respectively. It performs by detecting by.
상술한 바와 같은 종래의 변위측정장치는 광을 50대 50으로 나누기가 어렵고 더욱이 광축정렬이 어렵고 광학계구성이 복잡한 단점이 있다. 또한, 종래의 변위측정장치는 편광 빔 스플리터와 같은 고가의 부품이 사용되는 단점이 있다.As described above, the conventional displacement measuring apparatus has a disadvantage in that it is difficult to divide the light by 50 to 50, and furthermore, the optical axis alignment is difficult and the optical system configuration is complicated. In addition, the conventional displacement measuring apparatus has a disadvantage that expensive components such as polarizing beam splitters are used.
따라서, 본 발명의 기술적 과제는 상술한 단점을 해결할 수 있는 변위측정장치를 제공하는 데 있다.Therefore, the technical problem of the present invention is to provide a displacement measuring apparatus that can solve the above-mentioned disadvantages.
또한, 본 발명의 다른 기술적 과제는 상기 변위측정장치를 이용한 변위측정방법을 제공하는 데 있다.In addition, another technical problem of the present invention is to provide a displacement measuring method using the displacement measuring device.
도 1은 종래의 변위측정장치를 개략적으로 도시한 도면이다.1 is a view schematically showing a conventional displacement measuring device.
도 2a 및 도 2b는 각각 본 발명에 따라 투과형 및 반사형의 변위측정장치를 도시한 개략도이다.2A and 2B are schematic diagrams showing a transmissive and reflective displacement measuring apparatus according to the present invention, respectively.
도 3은 본 발명의 변위측정장치를 이용한 변위측정방법을 설명하기 위하여 도시한 흐름도이다.3 is a flowchart illustrating a displacement measuring method using the displacement measuring apparatus of the present invention.
도 4 및 도 5는 본 발명의 변위측정장치를 이용할 때 제1 회절격자의 움직임에 따른 광 세기변화, 1차 및 2차 미분회로 신호, TTL 신호 및 펄스신호를 나타낸 그래프이다.4 and 5 are graphs showing changes in light intensity, first and second differential circuit signals, TTL signals, and pulse signals according to the movement of the first diffraction grating when using the displacement measuring apparatus of the present invention.
상기 기술적 과제를 달성하기 위하여, 본 발명은 광원과, 상기 광원의 하부에 상기 광원으로부터 나온 광이 입사하는 제1 회절격자와, 상기 제1 회절격자를 통과한 광은 브래그 조건에 맞는 일정한 회절각을 갖는 ±m차 회절광으로 변경되며 상기 ±m차 회절광이 입사하도록 상기 제1 회절격자의 하부에 상기 제1 회절격자에 수직하게 위치하는 두 개의 거울과, 상기 거울의 하부에 상기 거울에 반사된 ±m차 회절광이 상기 회절각과 동일한 각도로 입사되고 상기 제1 회절격자와 간격이 같은 제2 회절격자와, 상기 제2 회절격자를 통과한 ±m차 회절광은 상기 제2 회절격자에 수직하게 회절되어 ±m'차 회절광으로 변경되며 상기 제2 회절격자의 하부에 상기 ±m'차 회절광의 위상차이로 인한 간섭광의 발생 및 세기 변화를 측정하는 광전센서를 포함하여 이루어진다. 상기 광원의 하부에 상기 광원으로부터 나온 광을 평행하게 조절하는 콜리메이션 렌즈를 더 구비할 수 있다.In order to achieve the above technical problem, the present invention provides a light source, a first diffraction grating into which light emitted from the light source enters a lower portion of the light source, and light passing through the first diffraction grating has a constant diffraction angle suitable for Bragg conditions. Two mirrors positioned at a lower portion of the first diffraction grating and perpendicular to the first diffraction grating so that the ± m-order diffracted light is incident to the ± m-d diffraction light having The second diffraction grating having the reflected ± m-diffraction light incident at the same angle as the diffraction angle and having the same distance from the first diffraction grating, and the ± m-th diffraction light passing through the second diffraction grating are the second diffraction grating. And a photoelectric sensor which is diffracted perpendicularly to and is changed to ± m 'order diffracted light and measures the generation and intensity change of interference light due to the phase difference of the ± m' order diffracted light under the second diffraction grating. All. The lower portion of the light source may further include a collimation lens for adjusting the light emitted from the light source in parallel.
또한, 본 발명은 광원과, 상기 광원의 하부에 상기 광원으로부터 나온 광이 입사하는 제1 회절격자와, 상기 제1 회절격자에 반사한 광은 브래그 조건에 맞는 일정한 회절각을 갖는 ±m차 회절광으로 변경되며 상기 ±m차 회절광이 입사하도록 상기 제1 회절격자의 상부에 상기 제1 회절격자에 수직하게 위치하는 두 개의 거울과, 상기 거울의 상부에 상기 거울에 반사된 ±m차 회절광이 상기 회절각과 동일한 각도로 입사되고 상기 제1 회절격자와 간격이 같은 제2 회절격자와, 상기 제2 회절격자를 통과한 ±m차 회절광은 상기 제2 회절격자에 수직하게 회절되어 ±m'차 회절광으로 변경되며 상기 제2 회절격자의 상부에 상기 ±m'차 회절광의 위상차이로 인한 간섭광의 발생 및 세기변화를 측정하는 광전센서를 포함하여 이루어진다. 상기 광원의 하부에 상기 광원으로부터 나온 광을 평행하게 조절하는 콜리메이션 렌즈를 더 구비할 수 있다.The present invention also provides a light source, a first diffraction grating in which light emitted from the light source enters a lower portion of the light source, and light reflected by the first diffraction grating has ± m-d order diffraction having a constant diffraction angle suitable for Bragg conditions. Two mirrors which are converted into light and positioned perpendicular to the first diffraction grating on top of the first diffraction grating such that the ± m-d order diffracted light is incident, and the ± m-d order diffraction reflected on the mirror on top of the mirror The second diffraction grating having the light incident at the same angle as the diffraction angle and having the same distance from the first diffraction grating, and the ± m-d order diffracted light passing through the second diffraction grating are diffracted perpendicularly to the second diffraction grating and ± and a photoelectric sensor which is changed to m 'diffraction light and measures generation and intensity change of interference light due to the phase difference of the ± m' order diffraction light on the second diffraction grating. The lower portion of the light source may further include a collimation lens for adjusting the light emitted from the light source in parallel.
본 발명의 다른 기술적 과제를 달성하기 위하여, 본 발명은 광원으로부터 광을 제1 회절격자에 입사시키는 단계와, 상기 제1 회절격자에 입사된 광을 반사 또는 통과시켜 일정한 회절각을 갖는 ±m차 회절광을 생성시키는 단계와, 상기 ±m차 회절광을 두 개의 거울에 입사시켜 반사시키는 단계와, 상기 두 개의 거울에 반사된 ±m차 회절광을 상기 회절각과 동일한 각도로 상기 제1 회절격자와 간격이 같은 제2 회절격자에 입사시키는 단계와, 상기 제2 회절격자에 입사되어 통과된 ±m차 회절광은 상기 제2 회절격자에 수직하게 간섭되어 ±m'차 회절광으로 변경시키는 단계와, 상기 제1 회절격자의 움직임에 따라 발생하는 ±m'차 회절광의 위상차이로 인한 간섭광의 세기변화를 광전변환시키는 단계와, 상기 광전변환된 전기신호를 1차 및 2차 미분회로를 이용하여 90도의 위상차를 갖는 두 개의 광전신호로 분리하는 단계와, 상기 두 개의 광전신호를 AD 변환 및 TTL 신호변환하여 90도 위상차가 있는 두 개의 TTL 신호를 생성하는 단계와, 상기 두 개의 TTL 신호의 엣지를 검출한 후 펄스 신호를 발생시켜 상기 제1 회절격자의 변위를 측정하는 단계를 포함한다.In order to achieve another technical object of the present invention, the present invention comprises the steps of incident light from the light source to the first diffraction grating, ± m difference having a constant diffraction angle by reflecting or passing the light incident on the first diffraction grating Generating diffracted light, reflecting the ± m-d order diffracted light by entering two mirrors, and diffusing the ± m-d order diffracted light reflected by the two mirrors at an angle equal to the diffraction angle Incident to a second diffraction grating having an interval equal to the second diffraction grating, and changing the ± m-diffraction light incident on the second diffraction grating and interfering with the second diffraction grating perpendicularly to change the ± m 'order diffracted light. And photoelectrically converting the intensity change of the interference light due to the phase difference of the ± m 'order diffracted light generated by the movement of the first diffraction grating, and using the first and second differential circuits of the photoelectrically converted electric signal. Separating two photoelectric signals having a phase difference of about 90 degrees, generating two TTL signals having a 90 degree phase difference by AD conversion and TTL signal conversion of the two photoelectric signals, and Generating an pulse signal after detecting an edge to measure a displacement of the first diffraction grating.
본 발명의 변위측정장치는 광학계의 구성요소가 간편하며, 광축 정렬이 용이하다. 또한, 본 발명의 변위측정장치는 2개의 회절격자를 이용하여 변위를 측정하기 때문에 가공 및 측정기기의 측정 분해능 및 정밀도를 높일 수 있다.Displacement measuring device of the present invention is a simple component of the optical system, the optical axis alignment is easy. In addition, since the displacement measuring device of the present invention measures the displacement using two diffraction gratings, it is possible to increase the measurement resolution and precision of the processing and measuring equipment.
이하, 첨부도면을 참조하여 본 발명의 실시예를 상세히 설명한다.Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention;
도 2a 및 도 2b는 각각 본 발명에 따라 투과형 및 반사형의 변위측정장치를 도시한 개략도이다.2A and 2B are schematic diagrams showing a transmissive and reflective displacement measuring apparatus according to the present invention, respectively.
구체적으로, 본 발명의 변위측정장치는 반도체 레이저와 같은 단색 광원(31)과, 상기 광원(31)의 하부에 상기 광원(31)으로부터 나온 광을 평행하게 조절하는 콜리메이션 렌즈(33)와, 상기 콜리메이션 렌즈(33)를 통과한 광이 입사하는 제1 회절격자(35)를 포함한다. 그리고, 상기 제1 회절격자(35)를 통과 또는 반사한 광은 브래그 조건에 맞도록 일정한 회절각을 갖는 ±m차 회절광(36a,36b)으로 변경되며 상기 ±m차 회절광(36a, 36b)이 입사하도록 상기 제1 회절격자(35)의 하부 또는 상부에 상기 제1 회절격자(35)에 수직하게 위치하는 두 개의 거울(37a, 37b)과, 상기 거울(37a, 37b)의 하부 또는 상부에 상기 거울(37a, 37b)에 반사된 ±m차 회절광(36a, 36b)이 상기 회절각과 동일한 각도로 입사되는 제2 회절격자(39)를 포함한다. 상기 제1 회절격자(35)는 제2 회절격자(39)와 간격이 동일하다. 상기 제2 회절격자(39)를 통과한 ±m차 회절광(36a, 36b)은 상기 제2 회절격자(39)에 수직하게 ±m'차 회절광(41a, 41b)으로 변경되어 중첩되며, 상기 제2 회절격자(41)의 하부 또는 상부에서 상기 ±m'차 회절광(41a, 41b)의 위상차이로 인한 간섭광의 세기 변화를 측정하는 광전센서(43)를 포함한다. 상기 광전센서(43)의 위치는 보강간섭이 일어나는 위치에 놓는다.Specifically, the displacement measuring apparatus of the present invention is a monochromatic light source 31, such as a semiconductor laser, a collimation lens 33 for adjusting the light emitted from the light source 31 in parallel below the light source 31, And a first diffraction grating 35 through which light passing through the collimation lens 33 is incident. The light passing or reflected through the first diffraction grating 35 is changed to ± m-diffraction light beams 36a and 36b having a constant diffraction angle to meet Bragg conditions, and the ± m-difference diffraction light beams 36a and 36b. ) Two mirrors (37a, 37b) perpendicular to the first diffraction grating (35a) on the lower or upper portion of the first diffraction grating (35), the lower or below the mirror (37a, 37b) The second diffraction grating 39 is incident on the upper side at the same angle as the diffraction angle of ± m-diffraction light beams 36a and 36b reflected by the mirrors 37a and 37b. The first diffraction grating 35 has the same spacing as the second diffraction grating 39. ± m-d diffraction light beams 36a and 36b passing through the second diffraction grating 39 are changed to and overlapped with ± m 'order diffraction light beams 41a and 41b perpendicular to the second diffraction grating 39, It includes a photoelectric sensor 43 for measuring the change in the intensity of the interference light due to the phase difference of the ± m 'order diffracted light (41a, 41b) in the lower or upper portion of the second diffraction grating (41). The photoelectric sensor 43 is positioned at the position where constructive interference occurs.
도 3은 본 발명의 변위측정장치를 이용한 변위측정방법을 설명하기 위하여 도시한 흐름도이고, 도 4 및 도 5는 본 발명의 변위측정장치를 이용할 때 제1 회절격자의 움직임에 따른 광 세기변화, 1차 및 2차 미분회로 신호, TTL 신호 , 펄스신호를 나타낸 그래프이다.3 is a flowchart illustrating a displacement measuring method using the displacement measuring apparatus of the present invention, and FIGS. 4 and 5 are light intensity changes according to the movement of the first diffraction grating when using the displacement measuring apparatus of the present invention; It is a graph showing the first and second differential circuit signal, TTL signal and pulse signal.
구체적으로, 광원으로부터 광을 제1 회절격자에 입사시킨다(스텝 50). 이어서, 상기 제1 회절격자에 입사된 광은 통과 또는 반사하여 브래그 조건에 맞도록 일정한 회절각을 갖는 ±m차 회절광을 생성시킨다 (스텝 52). 계속하여, 상기 ±m차 회절광을 두 개의 거울에 입사시켜 반사시킨다 (스텝 54). 다음에, 상기 두 개의 거울에 반사된 ±m차 회절광을 상기 회절각과 동일한 각도로 상기 제1 회절격자와 간격이 같은 제2 회절격자에 입사시킨다 (스텝 56). 상기 제2 회절격자를 통과한 ±m차 회절광은 상기 제2 회절격자에 수직하게 회절되어 ±m'차 회절광으로 변경된다 (스텝 58). 다시 말하면, 제1 회절격자의 변위에 따라 ±m'차 회절광의 위상차의 주기적인 변화가 발생되어 ±m'차 회절광이 서로 간섭이 일어난다.Specifically, light is incident on the first diffraction grating from the light source (step 50). Subsequently, the light incident on the first diffraction grating passes or reflects to generate ± m-th order diffracted light having a constant diffraction angle to match the Bragg condition (step 52). Subsequently, the ± m-diffraction light is incident on two mirrors and reflected (step 54). Next, the ± m-th order diffracted light reflected by the two mirrors is incident on the second diffraction grating equal to the first diffraction grating at the same angle as the diffraction angle (step 56). The ± m-th order diffracted light passing through the second diffraction grating is diffracted perpendicularly to the second diffraction grating and is changed to the ± m 'order diffracted light (step 58). In other words, a periodic change in the phase difference of the ± m 'order diffracted light occurs according to the displacement of the first diffraction grating, so that the ± m' order diffracted light interferes with each other.
이러한 상기 ±m'차 회절광의 위상차이로 인한 간섭광의 세기변화를 광전변환시킨다 (스텝 60). 여기서, ±1차 회절광을 이용한 제2 회절격자를 통과한 회절광의 광세기 변화는 다음의 수학식 1로 나타내어진다.The intensity change of the interference light due to the phase difference of the ± m 'order diffracted light is photoelectrically converted (step 60). Here, the change in the light intensity of the diffracted light passing through the second diffraction grating using the ± first order diffracted light is represented by the following equation (1).
여기서, x는 제1 회절격자의 변위를 나타내며, p는 회절격자의 회절격자 간격을 나타낸다.Here, x represents the displacement of the first diffraction grating, p represents the diffraction grating spacing of the diffraction grating.
상기 수학식 1에서 보듯이 간섭광의 세기는 회절격자의 변외 x가 회절격자의 간격 P만큼 이동하였을 경우 COS8π의 변화가 발생함으로 회절격자 P의 변위에 따라서 간섭광의 세기는 4 주기 변화가 발생하는데, 이는 도 4에 도시한 광신호(a)에서도 마찬가지로 나타난다. 즉 제1 회절격자의 변위 x가 회절격자의 간격 p에 해당하는 거리를 움직이는 동안 광세기(a)의 변화는 4주기의 변화가 발생함을 나타낸다.As shown in Equation 1, when the out of the diffraction grating x is shifted by the interval P of the diffraction grating, the change of COS8π occurs. As a result, the intensity of the interference light varies by four periods according to the displacement of the diffraction grating P. This is also shown in the optical signal a shown in FIG. That is, while the displacement x of the first diffraction grating moves a distance corresponding to the distance p of the diffraction grating, the change of the light intensity a indicates that the change of four periods occurs.
다음에, 상기 광전변환된 전기신호를 도 4 및 도 5에 나타낸 바와 같이 1차 및 2차 미분회로를 이용하여 90도의 위상차를 갖는 두 개의 광전신호(b, c)로 분리한다(스텝 62). 즉 1차 미분회로에 의한 광전신호(b)와 2차 미분회로에 의한 광전신호(c)로 분리된다. 이때, 상기 1차 및 2차 미분회로에 의한 두 개의 광전신호(b, c)의 주기는 광전센서의 광세기 변화주기와 동일하다.Next, the photoelectrically converted electrical signal is separated into two photoelectric signals b and c having a phase difference of 90 degrees using primary and secondary differential circuits as shown in FIGS. 4 and 5 (step 62). . That is, the photoelectric signal b by the first differential circuit and the photoelectric signal c by the second differential circuit are separated. At this time, the period of the two photoelectric signals (b, c) by the first and second differential circuits is the same as the light intensity change period of the photoelectric sensor.
이어서, 상기 두 개의 광전신호를 AD 변환 및 TTL 신호변환하여 90도 위상차가 있는 두 개의 TTL 신호를 생성한다 (스텝 64). 다음에, 도 5에 도시한 두 개의 TTL 신호(d, e)의 엣지를 검출하여 펄스신호(f)를 발생한 후 이를 검출하여 상기 제1 회절격자의 변위를 측정한다 (스텝 66). 이때, 펄스신호(f)의 간격은 제1 회절격자의 이동거리가 p/2인 경우 p/8의 주기의 신호를 얻을 수 있다. 결국 P의 회절격자 간격을 갖는 회절격자를 이용하여 p/16의 분해능을 갖는 스케일을 제작할 수 있다.Subsequently, the two photoelectric signals are subjected to AD conversion and TTL signal conversion to generate two TTL signals having a 90 degree phase difference (step 64). Next, the edges of the two TTL signals d and e shown in FIG. 5 are detected to generate a pulse signal f, and then detected to measure the displacement of the first diffraction grating (step 66). At this time, the interval of the pulse signal f can obtain a signal having a period of p / 8 when the moving distance of the first diffraction grating is p / 2. As a result, a scale having a resolution of p / 16 may be manufactured using a diffraction grating having a diffraction grating interval of P.
결과적으로, 본 발명은 동일한 회절격자 간격 p를 갖는 두 개의 회절격자를 사용함으로써 단색광이 제1 회절격자에 입사하여 브래그 조건에 의해 ±m차 회절광이 대칭적으로 만들어지며, ±m차 회절광이 수직하게 놓여 있는 거울에 의해 반사되어 제2 회절격자에 각각의 ±m차 회절광의 회절각과 동일한 각도로 입사되어 ±m'차 회절광을 만든다. ±m'차 회절광은 위상차이에 의해 보강상쇄간섭이 이루어지며 회절격자들의 움직임에 따라 간섭광의 명암이 주기적인 변화가 발생되어 광전센서를 이용하여 간섭광의 명암변화를 측정함으로써 회절격자의 변위를 측정할 수 있게 된다.As a result, in the present invention, by using two diffraction gratings having the same diffraction grating interval p, monochromatic light is incident on the first diffraction grating so that ± m-d order diffracted light is symmetrically made by Bragg conditions, ± m-d order diffracted light Reflected by this vertically placed mirror, it is incident on the second diffraction grating at an angle equal to the diffraction angle of each ± m-order diffracted light to produce ± m'-order diffracted light. The retardation cancellation interference is caused by the phase difference of ± m 'order diffraction light, and the intensity of interference light changes periodically according to the movement of the diffraction gratings. You can measure it.
상술한 바와 같은 본 발명은 변위측정장치는 광학계의 구성요소가 간편하며, 광축 정렬이 용이하다. 또한, 본 발명은 고분해능의 직선 또는 각도 변위측정을 행함으로써 가공 및 측정기기의 정밀도를 높일 수 있다.The present invention as described above, the displacement measuring device is a simple component of the optical system, the optical axis alignment is easy. In addition, the present invention can improve the precision of processing and measuring equipment by performing a high resolution linear or angular displacement measurement.
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