WO2018013003A1 - Procédé par diffraction pour mesurer les dimensions linéaires d'un objet - Google Patents

Procédé par diffraction pour mesurer les dimensions linéaires d'un objet Download PDF

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Publication number
WO2018013003A1
WO2018013003A1 PCT/RU2017/000378 RU2017000378W WO2018013003A1 WO 2018013003 A1 WO2018013003 A1 WO 2018013003A1 RU 2017000378 W RU2017000378 W RU 2017000378W WO 2018013003 A1 WO2018013003 A1 WO 2018013003A1
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WO
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Prior art keywords
size
signal
measuring
amplitude
diffraction pattern
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PCT/RU2017/000378
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English (en)
Russian (ru)
Inventor
Георгий Дмитриевич ФЕФИЛОВ
Валерий Юрьевич ХРАМОВ
Original Assignee
федеральное государственное автономное образовательное учреждение высшего образования "Санкт-Петербургский национальный исследовательский университет информационных технологий, механики и оптики" (Университет ИТМО)
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Application filed by федеральное государственное автономное образовательное учреждение высшего образования "Санкт-Петербургский национальный исследовательский университет информационных технологий, механики и оптики" (Университет ИТМО) filed Critical федеральное государственное автономное образовательное учреждение высшего образования "Санкт-Петербургский национальный исследовательский университет информационных технологий, механики и оптики" (Университет ИТМО)
Publication of WO2018013003A1 publication Critical patent/WO2018013003A1/fr

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Classifications

    • 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
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • 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
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • G01B11/028—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness by measuring lateral position of a boundary of the object

Definitions

  • the invention relates to measuring and control equipment and can be used to measure the linear (transverse) size of various objects and products, for example, microwires or fibers, gaps or slots with micron sizes, microholes and round screens, as well as suspensions of microparticles or biological suspensions.
  • linear (transverse) size of various objects and products for example, microwires or fibers, gaps or slots with micron sizes, microholes and round screens, as well as suspensions of microparticles or biological suspensions.
  • the interval between the extreme points corresponding to the intensity minima of the maxima (lobes) of the diffraction pattern is usually used.
  • extreme points are shifted by different values, as a result of which the interval between them changes, which leads to an increase in the measurement error.
  • a diffraction method for measuring the linear size of an article is known, based on recording the intensity of diffraction distribution at fixed points. The size of the measured product is judged by the difference in intensities at these points of the diffraction pattern.
  • a known diffraction method for measuring the linear size of an article is that the measured object is irradiated with coherent radiation, a Fraunhofer diffraction pattern is obtained, the intensities of the maxima of which are smoothed out, raster modulation of the resulting spatial signal is carried out with a successively varying frequency, the amplitude change of which, after interaction with a periodic spatial signal, describes the frequency amplitude spectrum of the spatial signal, fix the value of the frequency of the module At the moment of maximum amplitude corresponding to the fundamental harmonic of the spatial signal, the size of the monitored product is judged by the value of the fixed modulation frequency.
  • Evseenko N.I. Kozachok A.G., Solodkin Yu.N., Analysis of diffraction methods for measuring linear dimensions. Metrology, 1984, N ° 2, pp. 17-283
  • the disadvantage of this diffraction method of measurement is also the dependence of the measurement result on the uneven distribution of the intensity of the laser radiation in the plane of the measured object.
  • the known diffraction method for measuring the linear size of the product which consists in the fact that the measured object is irradiated with coherent radiation, a Fraunhofer diffraction pattern is obtained, the linear size of the object is judged by the coordinates of the inflection points of the main maximum of the diffraction pattern.
  • a Fraunhofer diffraction pattern is obtained, the linear size of the object is judged by the coordinates of the inflection points of the main maximum of the diffraction pattern.
  • the disadvantage of this method is the dependence of the position of the inflection points of the main maximum of the diffraction pattern and the interval between them on the uneven distribution of the amplitude of the irradiating field in the plane of the measured object.
  • the position of the singular points and the characteristic size between them at the main maximum most of all depend on the uneven distribution of the amplitude of the irradiating field in the plane of the measured object.
  • the position of the inflection points of the main maximum of the diffraction pattern and the characteristic size of the main maximum of the diffraction pattern also depend on the shape of the measured object.
  • the size of the main maximum of the diffraction pattern of objects of rectangular and round shape of the same size differs by more than 20%, which makes it impractical to use this technique to measure objects whose shape is a priori unknown, for example, biological suspensions or suspensions of microparticles.
  • a diffraction method for measuring the linear size of the product which consists in sending a monochromatic coherent light beam to the product, forming a diffraction pattern from the product, which is scanned with simultaneous conversion into a temporary oscillating electrical measuring signal .., equalizing the amplitude of the variable component in it.
  • the size of the measured product is judged by the period of the electrical signal, which is directly proportional to the size of the diffraction maximum (lobe) and inversely proportional to the linear size of the measured object.
  • An oscillating electric signal with a uniform amplitude, obtained by recording the diffraction pattern, can be periodic only under ideal conditions. First of all, the amplitude distribution in the plane of the measured object should be uniform.
  • the source of coherent monochromatic radiation are lasers operating on the main type of vibration TEM00, with an almost Gaussian law of the distribution of the amplitude in the beam cross section.
  • the laser diffractometer operates in the range of changing the size of the object (with a magnification of up to 100, from 5 to 500 microns.)
  • the ratio of the size of the Gaussian beam to the size of the object if the size of the Gaussian beam is constant).
  • a change in the uneven distribution of the amplitude of the irradiating field in the plane of the controlled object The larger the size of the object, the greater the uneven distribution of the amplitude of the irradiating field in its plane.
  • the diffraction pattern Due to the uneven distribution of the amplitude of the irradiating field in the plane of the measured object, the diffraction pattern is nonlinearly deformed. As a result, there is a shift by different values of the extreme points in the recorded oscillating signal and a change in the intervals between them.
  • the resulting error in measuring the size of an object can be more than 1% (Mitrofanov A.S., Fefilov G.D. Evaluation of the effect of the divergence of laser radiation and the position of the measured hole in a Gaussian beam on the error of the diffraction measurement method // Izvestiya Vuzov. Instrument Engineering, 1989. T. 32. 7. P.
  • the problem to which this invention is directed is to ensure maximum accuracy in measuring the size of an object without increasing the transverse size of the laser beam.
  • the problem is solved by achieving a technical result, which consists in reducing the influence of the aperiodicity of the oscillating electric signal.
  • the diffraction method of measuring the linear size of the object which consists in sending a monochromatic coherent light beam to the object to be measured, forms a diffraction pattern from the object, which is scanned with simultaneous conversion of the intensity distribution in it into a temporary oscillating electric signal, amplitude the variable component of which is maintained constant by changing the power of the light beam directed at the product, synchronously with scanning the diffraction pattern, it differs in that the inflection points are recorded in the received oscillating electric signal, and the linear size of the object is judged by the time interval between the even inflection points.
  • the claimed diffraction method for measuring the linear size of an object is implemented using a device, a block diagram of which is shown in FIG. 1.
  • the device consists of a laser 1, a measured object 2, a Fourier lens 3, a combined photodetector and a scanning device 4, a position sensor 5, a unit for generating a laser radiation power control signal 6, a first signal differentiator 7, a second signal differentiator 8, a comparator 9, block 10 allocation of measurement information.
  • the device operates as follows: they direct a beam of monochromatic coherent radiation generated by laser 1 to the measured object 2 (usually a HE-NE laser operating on the main mode TEM 0 THER is used). Using the Fourier lens 3, a Fraunhofer diffraction pattern is formed, a fragment of which is converted into a temporal oscillating electric signal using combined photodetector and scanning device 4. The amplitude of the oscillating electrical signal is kept constant using the method of amplitude spatial-temporal filtering. This technique is implemented using a laser 1, associated with the scanning system 4 of the position sensor 5, block 6 of the formation of the signal for controlling the laser radiation power.
  • the clock pulse generated at the time of starting the scanning of the diffraction pattern by block 5 is fed to the input of block 6, which generates a control signal the radiation power of laser 1, changing it from the threshold of generation to the maximum value from the moment of beginning to the moment of the end of scanning the diffraction pattern, after which the radiation power of laser 1 decreases to the threshold of generation.
  • the oscillating electric signal coming from the output of the photodetector is differentiated twice, with the help of differentiated signal differentiators 7 and 8.
  • the inflection points are fixed by the transition through zero of the second derivative of the oscillating signal.
  • the signal from the output of the second differentiator 8 is fed to the input of the comparator 9.
  • a sequence of pulses is formed, the leading and trailing edges of which occur at the moment the second derivative of the oscillating signal passes through zero, which correspond to the inflection points of the signal.
  • the pulse train is fed to the input of the block 10 for extracting measurement information consisting, for example, of a decimal counter and a trigger, and a single pulse is generated at the output of block 10, the leading and trailing edges of which correspond to even points of inflection of the oscillating signal.
  • the duration of this pulse is inversely proportional to the size of the controlled object and weakly depends on the uneven distribution of the amplitude of the irradiating field in the plane of the measured object.
  • FIG. 2 shows the waveforms at the output of the blocks of the measuring device.
  • Fig. 2 a are shown: a - control signal of the radiation power of the laser 1; b, c, e show the intensity distribution in the diffraction pattern with increasing laser radiation power at the moments of scanning of the first (b), second (c), third (d) and fourth (e) maxima of the diffraction pattern.
  • FIG. 26 shows an oscillating signal after optimal filtering and numbered inflection points in it.
  • FIG. 2c shows the first derivative of the oscillating signal.
  • FIG. 2d shows the second derivative of the oscillating signal.
  • FIG. 2e shows a pulse whose leading and trailing edges correspond to even points of inflection of the oscillating signal. This impulse is the selected measurement information about the size of the controlled object.
  • the dimensionless parameter a a / w e was varied in the range from 0 to 0.5 with a step of 0.1, and the following were calculated:
  • the achieved decrease in the influence of the aperiodicity of the electric signal provides, in comparison with the prototype, a higher accuracy of measuring the size of microobjects with optimal using the energy of laser radiation, transforming the measuring signal.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)
  • Length Measuring Devices By Optical Means (AREA)

Abstract

L'invention concerne des équipements de mesure et de contrôle et peut être utilisée pour mesurer la taille linéaire (transversale) de différents objets, par exemple, d'un fil métallique ou fibre microscopique, des fentes ou des interstices, des écrans de feuille ronde, ainsi que de suspensions de microparticules et des suspensions biologiques. L'objectif visé par l'invention consiste à réduire sensiblement l'effet sur les résultats de mesure de la taille de l'objet de l'irrégularité de répartition de l'amplitude du champ irradiant dans le plan de l'objet mesuré. L'objectif visé est résolu au stade de calcul des informations de mesure grâce à l'utilisation des points de pli dans le signal oscillant qui apparait lors de l'enregistrement du tableau de diffraction dont le position est robuste par rapport à la variation de l'irrégularité de répartition de l'amplitude du champ irradiant dans le plan de l'objet mesuré.
PCT/RU2017/000378 2016-07-13 2017-05-31 Procédé par diffraction pour mesurer les dimensions linéaires d'un objet WO2018013003A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
RU2016128651 2016-07-13
RU2016128651A RU2629895C1 (ru) 2016-07-13 2016-07-13 Дифракционный способ измерения линейного размера объекта

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WO2018013003A1 true WO2018013003A1 (fr) 2018-01-18

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU521456A1 (ru) * 1974-08-30 1976-07-15 Северо-Западный Заочный Политехнический Институт Фотоэлектрический способ измерени линейных размеров издели и устройство дл реализации способа
SU1357701A1 (ru) * 1985-07-12 1987-12-07 Ленинградский Институт Точной Механики И Оптики Дифракционный способ измерени линейного размера издели и устройство дл его осуществлени
EP0383832B1 (fr) * 1987-11-26 1992-04-29 FARDEAU, Jean-Francois Procede de mesure de diametres de fils ou de profils ou pieces circulaires par diffraction de rayons lumineux et dispositif pour la mise en oeuvre de ce procede
JP2000304507A (ja) * 1999-04-21 2000-11-02 Citizen Watch Co Ltd 回折格子の回折光干渉を用いた寸法測定装置

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU521456A1 (ru) * 1974-08-30 1976-07-15 Северо-Западный Заочный Политехнический Институт Фотоэлектрический способ измерени линейных размеров издели и устройство дл реализации способа
SU1357701A1 (ru) * 1985-07-12 1987-12-07 Ленинградский Институт Точной Механики И Оптики Дифракционный способ измерени линейного размера издели и устройство дл его осуществлени
EP0383832B1 (fr) * 1987-11-26 1992-04-29 FARDEAU, Jean-Francois Procede de mesure de diametres de fils ou de profils ou pieces circulaires par diffraction de rayons lumineux et dispositif pour la mise en oeuvre de ce procede
JP2000304507A (ja) * 1999-04-21 2000-11-02 Citizen Watch Co Ltd 回折格子の回折光干渉を用いた寸法測定装置

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