WO2009105904A1 - Verfahren und vorrichtung zur auswertung einer interferometrischen messgrösse - Google Patents
Verfahren und vorrichtung zur auswertung einer interferometrischen messgrösse Download PDFInfo
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- WO2009105904A1 WO2009105904A1 PCT/CH2009/000044 CH2009000044W WO2009105904A1 WO 2009105904 A1 WO2009105904 A1 WO 2009105904A1 CH 2009000044 W CH2009000044 W CH 2009000044W WO 2009105904 A1 WO2009105904 A1 WO 2009105904A1
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- cavity
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
- G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
- G01K11/3206—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres at discrete locations in the fibre, e.g. using Bragg scattering
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B9/00—Measuring instruments characterised by the use of optical techniques
- G01B9/02—Interferometers
- G01B9/02041—Interferometers characterised by particular imaging or detection techniques
- G01B9/02044—Imaging in the frequency domain, e.g. by using a spectrometer
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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
- G01B9/00—Measuring instruments characterised by the use of optical techniques
- G01B9/02—Interferometers
- G01B9/0209—Low-coherence interferometers
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
- G01L9/0041—Transmitting or indicating the displacement of flexible diaphragms
- G01L9/0076—Transmitting or indicating the displacement of flexible diaphragms using photoelectric means
- G01L9/0077—Transmitting or indicating the displacement of flexible diaphragms using photoelectric means for measuring reflected light
- G01L9/0079—Transmitting or indicating the displacement of flexible diaphragms using photoelectric means for measuring reflected light with Fabry-Perot arrangements
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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
- G01B2290/00—Aspects of interferometers not specifically covered by any group under G01B9/02
- G01B2290/25—Fabry-Perot in interferometer, e.g. etalon, cavity
Definitions
- the invention relates to a method for evaluating a measured variable with a measuring cell according to the features of patent claims 1 and 2, and to a measuring arrangement according to the preamble of claim 16.
- the invention relates to an evaluation method in connection with a fiber-optic interferometric sensor measuring system for measuring measured variables such as pressure, temperature, strain and of optical powers.
- vacuum pressures should be particularly easy and accurate to detect.
- Fabry-Perot Fabry-Perot
- FP Fabry-Perot
- the optical path length difference is calculated from the product of the refractive index of the material through which the light moves and the geometric path difference that the light travels.
- an optical path length difference may, for example, change as the distance between two membranes forming the Fabry-Perot sensor cavity changes in response to pressure, or this distance varies due to material expansion due to temperature changes. However, it can also change, for example, by changing the optical properties (refractive index) of a material which is located in the cavity or forms the cavity.
- a measuring system consists of a Fabry-Perot cavity, which forms the actual sensor, a suitable evaluation unit and a light source.
- the light source is a broadband or white light source with a short coherence wavelength
- WLI white light interferometry
- the sensor cavity is connected to the evaluation unit with an optical waveguide.
- the light from the light source is guided via optical fiber to the sensor cavity. In this it is modulated, depending on the optical path length or the size to be measured.
- the modulated light is then returned to the evaluation unit via the same or a separate second optical waveguide and evaluated therein.
- the evaluation can basically be realized in two different ways. For this purpose either an interferometer or a spectrometer is used.
- spectrometers Today's evaluation units use high-quality spectrometers. These have a resolution of better than 1 nm and use line sensors with more than 3500 individual sensor elements (pixels). For each measurement cycle, all sensor elements must be read and digitized. The resulting amount of data is proportional to the number of sensor elements and thus also determining the shortest possible cycle time. This is at the currently used spectrometers at 50ms, which corresponds to a maximum refresh rate of 20Hz. The individual prices for such spectrometers are high, always well over $ 1'000.- (typically $ 1'499.- to $ 1'899.-, depending on the model). Fizeau and polarization interferometers, as shown schematically in FIGS. 1 and 2, are largely equivalent in terms of their structure.
- FIG. 1 The construction of a Fizeau interferometer is shown schematically in FIG. 1 (see also US Pat. No. 5,392,117, Belleville). With the Fizeau interferometer, this wedge must be provided with reflection layers.
- FIG. 2 The structure of a polarization interferometer is shown schematically in FIG. 2 (see also US Pat. No. 7,259,828 B2, Duplain).
- the wedge 30 in the polarization interferometer uses polarizers instead of the reflective layers.
- Such a wedge with the necessary layers or polarizers is complex and therefore expensive to produce and has undesirable dispersion effects which influence the resulting interferogram and reduce the achievable measurement accuracy.
- the optical path length in the wedge is temperature dependent. This dependence can be (partially) compensated, but nevertheless has a detrimental effect on the achievable accuracy and means additional expenditure for the realization.
- both interferometer principles provide only relative readings, ie both must be calibrated during production to provide absolute readings.
- the measuring range is defined by the wedge and thus fixed.
- the largest measurable optical path length is determined by the largest thickness and the smallest measurable optical path length through the smallest thickness of the wedge.
- the achievable resolution depends, among other things, on the contrast and the signal-to-noise ratio of the measurement signal, which in turn depend on the depth of modulation of the sensor and the length and / or length of the signal.
- the modulation depth ratio of modulated to non-modulated light
- a reflection of about 25% is ideal for the cavity, but in practice this can only be done very reaching optically effective coatings.
- FIG. 3 shows the schematic structure of a corresponding measuring system.
- FFT direct Fast Fourier Transformation
- bandpass filter inverse FFT
- adding up the phase and then determining the measured value from a lookup table.
- DSP Digital Signal Processor
- the measured spectrum must be normalized, which in addition to the actual measuring sensor 5 requires a second reference sensor 31.
- FIG. 4 shows the schematic structure of such a measuring system.
- the alternative calculation method is based on the correlation of the measured spectrum with predicted and stored theoretical spectra.
- a significant disadvantage in this case is the memory 34 necessary for the storage of the precalculated spectra, as well as the computation time necessary for calculating the correlation 33 of the corresponding arithmetic unit 32.
- the achievable measurement accuracy depends on the number of stored spectra and thus on the available storage space but also on the available computing time.
- the tracking method does not work anymore, because then tracking is no longer possible. If you want to use the meter in a stable control loop, you must, in order to be able to guarantee stability, assume the maximum measuring cycle time or response time of the meter. For the reasons just mentioned (fast signal change, signal jumps) the tracking therefore has no influence on the minimum measurement cycle time.
- the spectrometer-based described methods are unsuitable for industrial implementation, because they require too many resources (memory, computing power), do not allow fast rule applications and are too expensive.
- the object of the present invention is to determine the absolute optical path length difference in this sensor simply and quickly, accurately and with high resolution from the optical spectrum of an interferometric sensor (Fabry-Perot, for example) measured by means of a simple spectrometer. Evaluation units which are based on this method must be economically producible.
- an interferometric sensor Fabry-Perot, for example
- a measuring cell contains a cavity for evaluating a measured variable with which an optical path length difference (dGap) is generated for light. Light is therefore coupled to the cavity and reflected within this and decoupled again. The optical path length difference in this cavity changes in accordance with the variation of the measured variable.
- the evaluation of the measured variable comprises the following steps:
- the present invention possible to use an arithmetic function in an arithmetic unit from the spectrum directly, without detours, to determine the interferogram, which as output signal directly the length unit includes, which corresponds to the optical path length difference and thus the size to be measured.
- the arithmetic function preferably contains a cosine function at least to a first approximation.
- the cosine function makes it possible to greatly simplify the entire signal processing and the measuring arrangement. It goes without saying that this also includes all pure trigonometrically reshaped representations of a cosine function, which are then represented, for example, with the other trigonometric functions, such as sine, tangent, cotangent functions or corresponding approximations.
- the decoupling of at least a portion of the light reflected from the cavity with at least one further or more optical waveguides takes place, which are arranged separately next to the feeding optical waveguide.
- a plurality of optical fibers for coupling the light into the cavity and for coupling out the light reflected from the cavity which are arranged, for example, together in a mixed bundle of fibers leading in and out.
- the reflected light is supplied to an optical spectrometer.
- an optical fiber and a coupler is less expensive, gives more accurate results and is therefore preferred.
- the present invention is particularly suitable for the very precise detection of vacuum pressures, in particular with so-called membrane vacuum measuring cells, in which the cavity is integrated directly into the measuring cell and the membrane is deformed depending on the vacuum pressure to be measured and this directly closes the cavity and by their deformation the signal to be measured determines the optical path length difference.
- Such measuring cells can be constructed particularly compact and, because of the integrally suitable and well-coordinated measuring concept, allow particularly precise and reproducible measurements over large measuring ranges in economic production.
- Another significant advantage is that such measuring cells can essentially be made of ceramic materials such as alumina and / or sapphire, including the measuring membrane, whereby such a measuring cell is very resistant to chemically aggressive vacuum processes even at high temperatures.
- the optical readout method supports the suitability for high temperatures and is also insensitive to interfering electrical or electromagnetic influences, which supports the high measuring sensitivity and stability of such a measuring cell.
- vacuum processes for example in the semiconductor industry, such particularly high demands are becoming increasingly important.
- FIG. 1 is a schematic diagram of a Fizeau interferometer according to the prior art
- FIG. 2 is a schematic diagram of a polarization interferometer according to the prior art
- 3 shows an optical interferometric measuring system based on an optical spectrometer with a second reference sensor for the standardization of the measuring signal according to the prior art
- FIG. 4 shows an optical interferometric measuring system based on an optical spectrometer with a computing unit with memory for correlation with reference spectra for determining the measured variable according to the prior art
- FIG. 2 is an enlarged detail of the interferogram of FIG. 7.
- FIG. 8 shows a measuring arrangement with a preferred vacuum membrane measuring cell as measuring sensor
- FIG. 9 shows a measuring arrangement with a temperature measuring cell as a measuring sensor.
- FIGS. 1 to 4 schematically depict known measurement systems based on optical interference principles which have already been described in the introduction.
- FIG. 5 shows a typical structure of a preferred membrane-based Fabry-Perot measuring system.
- the system consists of the evaluation unit 13 and the sensor 5 which is connected by means of optical waveguide 4 to the evaluation unit 13.
- Light 1 from a white light source 2 is fed via coupler 3 and optical waveguide 4 to the measuring sensor 5, designed as a Fabry-Perot sensor 5 with a cable. vity 11, and modulated in it as a function of the quantity to be measured.
- the modulated light is conducted via the same optical waveguide 4 and coupler 3 to an optical spectrometer 6. This generates an output signal, the spectrometer signal 8, by measuring altogether m ⁇ intensity values s ⁇ ( ⁇ m ) at the various wavelengths ⁇ m .
- Each value s ⁇ ( ⁇ m ) corresponds to the measured intensity at the wavelength ⁇ m .
- the optical spectrum is picked up, for example with a line sensor 7 and converted into a corresponding electrical signal and processed to the spectrometer signal 8.
- the spectrometer line sensor output signal 8, or the spectrometer 8 is at the output of the spectrometer 6 with a spectro - Meterignaltechnisch guided via a corresponding electrical interface to a computing unit 9, where this signal is converted with a computing function.
- the arithmetic unit 9 transmits the converted signal to the output unit 10, where the signal can be processed in the desired form, for example as an analog or digital electrical or optical signal for further use.
- the cavity 11 is formed by two mirrors 19, 19 'which are arranged at a geometrical mirror spacing (d geo ).
- these mirrors 19, 19 ' is designed to be partially transparent to the light.
- a portion of the light 1 is introduced into the cavity 11 via one of the partially transmissive mirrors 19, and this portion is now reflected back and forth between the partially transmissive mirrors 19 and 19 ', with part of the light coming out at each reflection on the partially transparent mirror 19 the cavity is coupled out, which interferes with the reflected there, uncoupled portion of the light 1 and depending on the different distance of the two light components traveled distance corresponding to an integer multiple of the optical path length difference (dcap), which through the cavity or the geometric distance (d geo ) of the two partially transmitting mirror 19, 19 'is defined.
- dcap optical path length difference
- the cavity 11 consists of a material with the refractive index 1 (eg air or vacuum), then this optical path length difference (d ⁇ a p) is approximately twice as large as the spatial Gelabstand (d geo ) - It is favorable if for the metrological tasks to be solved here, the cavity 11 is formed such that there is an optical path length difference (dc a p) is formed, which is in the range of 10.0 microns to 400 microns, preferably in Range from 20.0 ⁇ m to 60.0 ⁇ m.
- Partially transparent mirrors may be formed, for example, as coated surfaces. However, depending on the substrate material, such as, for example, glass or sapphire, they can also serve directly as partially transmissive mirrors if the surface is suitable.
- the measured quantity to be measured 12 of the measuring cell 5 changes the mirror spacing d geo accordingly. This change is subsequently detected with the present arrangement and method, and enables a precise and reproducible reproduction of the measured quantity 12, which is consequently available at the output 10 of the arrangement in processed form.
- any commercially available spectrometer covering the spectral range of the light source and having a resolution of better than 4 nm FWHM (fill width at half maximum) can be used.
- the spectrometer sensor element 7 can likewise be a commercially available line sensor (charge coupled device (CCD), complementary metal oxide semiconductor (CMOS), photo diode array (PDA)) with at least 256 sensor elements (pixels).
- CMOS array with 512 sensor elements is used.
- the measured spectrometer signal 8 is then converted by means of a computation function by the arithmetic unit 9 directly to an interferogram l (d), l '(d) and from its intensity profile the position of the respective amplitude extreme value.
- Ux t r e mai determined and these respective position directly represents the value for the optical path length difference (dGap) in the cavity, which contains the measurement quantity 12.
- the arithmetic function for conversion into the absolute interferogram preferably and at least to a first approximation contains a cosine function.
- the denominator and the 1st term in the counter are provided, for example, for normalization or scaling of the signal.
- these additional functions are not necessary and the formula (1) can be simplified to: m ⁇
- this basic function with the relevant cosine function can additionally be combined or superimposed with further arithmetic functions if further signal adjustments are desired.
- Each interpolation point k corresponds to an optical path difference d k , ie the interferogram is calculated between the values d min and d max for a total of k 0 interpolation points.
- d k namely:
- spacings in the range from 5.0 ⁇ m to 200 ⁇ m are preferred for mirror spacings (dg eo ), preferably in the range from 10.0 ⁇ m to 30.0 ⁇ m.
- the optical path length difference corresponds to exactly twice the mirror spacing. This assuming that the light 1 exactly and exclusively perpendicular to the cavity 11, and the mirror surfaces 19, 19 ', incident and is reflected by these.
- the exact position of the amplitude extreme value lex t re ma i of the interferogram l (dk) or l '(d k ) is most easily determined by means of a quadratic approximation (quadratic fit).
- Vertex can be determined exactly by zeroing the 1st derivative
- n represents the optical refractive index of the material in the sensor cavity 11 and C is a correction factor, which takes into account the influence of the angle of incidence of the light in the sensor cavity 11 as well as the corresponding intensity distribution of this light over all angles of incidence.
- the mirror spacing as well as the optical path length difference can be determined absolutely and directly without detours via correlations in the corresponding physical unit of length such as, for example, nanometers [nm].
- C is calculated to be 0.987887.
- a value for C of 0.999241 results.
- formula (5) can now be solved for the size of interest.
- the geometric distance d geo of the cavity 11 changes as a function of the measured variable 12 to be measured, for example, the pressure 12 to be measured.
- the cavity 11 is normally filled with air or evacuated.
- the refractive power n can be assumed to be 1.
- this is independent of the pressure to be measured and the formula (5) can be dissolved after dgeo and you get directly a measure of the pressure.
- the algorithm is implemented on an FPGA, it can easily be executed within much less than 1ms and thus the necessary computation time has no influence on the system cycle time. This is now determined by the necessary integration time of the line sensor element 7 (CCD array) in the spectrometer 6.
- line sensor element 7 CCD array
- spectrometer 6, light guide 4, coupler 3 a commercially available white LED 2 (from year 2007) as a light source and the simplest possible Fabry-Perot sensor 5 (with an uncoated cavity) can be a minimum integration time of 1ms straight still reach meaningful.
- spectrometers which have a resolution of substantially better than 1 nm FWHM. These need only have a minimum resolution of better than 4nm FWHM and can therefore be made much cheaper and smaller. With such simple spectrometers, however, it is still possible, for example, optical path length differences (dc a p) of example
- the spectrometers 6 are equipped with line sensors 7, which typically have 3,648 sensor elements (pixels). For each measurement cycle, all sensor elements must be read and digitized. The resulting amount of data is proportional to the number of sensor elements and thus also determining the shortest possible cycle time. This is at the currently used spectrometers at 50ms, which corresponds to a maximum refresh rate of only 20Hz.
- the method according to the invention makes it possible to use spectrometers with line sensors 7 with only 512 sensor elements. This considerably reduces the amount of data and cycle times of less than 1 ms or refresh rates of greater than IkHz can be achieved. This is a significant advantage over the state of the art (50ms or 20Hz), as it allows, inter alia, faster and more stable control systems to be constructed in which the optical measuring principle serves to detect the actual value. (eg flow control or mass flow controller).
- a further advantage of the invention is also that the measuring system can be easily adapted to different cavities (optical path length differences) as well as to the desired resolution ( ⁇ d) by appropriate software selection of the calculation range (d min , d max ). For interferometer-based systems, this is only possible by changing the hardware (thickness of the wedge 30) and in the known spectrometer-based systems have new Reference data for the correlation calculation are loaded into the memory. Thanks to the method according to the invention, it is therefore very easy to first drive a "coarse scan" over a large area (large d max -d min ) with poor resolution (large ⁇ d) to obtain the approximate position of the amplitude extreme value Ux tr em a to determine i.
- the already mentioned prior art methods are based on the correlation method.
- the measured spectrum must each be subjected to a Fast Fourier Transformation (FFT).
- FFT Fast Fourier Transformation
- the result of this FFT is then correlated with the stored values to calculate the measured value.
- an FFT and a subsequent correlation are always necessary.
- the calculation effort for determining the FFT from the measured spectrum corresponds to that which is necessary for calculating the interferogram according to the method according to the invention.
- the computational effort for the correlation is completely eliminated in the inventive procedure.
- the method according to the invention thus requires less computing time and thereby enables shorter measuring cycle times and faster response times. This, in turn, enables faster and more stable regulator applications compared to the prior art.
- fast signal changes or signal jumps can be better detected and tracked.
- the computing time can easily be reduced below 1 ms, ie the system cycle time is no longer determined by the computing time of the method but by the necessary integration time of the line sensor element 7 of the spectrometer 6, which of the available light power at the Line sensor element 7 and on its sensitivity and its noise properties depends.
- the interferogram calculation described in (1) and (1 ') already causes a strong reduction of the signal noise due to the summation used. Thanks to the fast measurement cycle time, additional filter functions such as moving average without increasing the response time of the meter over charge. With such filter functions, e.g. the resolution can be further increased or the minimum requirements for the necessary signal-to-noise ratio (signal quality) can be further reduced. Thus even longer connecting cables 4 between measuring sensor 5 and evaluation unit 13 can be used and the requirements for the tolerances of the measuring sensor 5 can be further reduced, which in turn leads to even simpler, cheaper and more robust or reliable measuring sensors ,
- the cavity 11 of the Fabry-Perot measuring sensors 5 must be to increase the contrast resp. the signal-to-noise ratio for the partially transmissive mirrors are coated.
- the method according to the invention now allows the use of uncoated cavities 11, i.
- the Fresnel reflection of about 4% of a normal glass surface already suffices for the formation of a partially transparent mirror.
- a further advantage of the method according to the invention is the fact that, as a result, one obtains directly the absolute optical path length difference (d Ga p) in a physical path length unit, eg nm.
- a physical path length unit eg nm.
- the only requirement for this is the use of a calibrated (commercially available) spectrometer 6.
- All evaluation units based on the known interferometer principle must be calibrated compulsorily so that an assignment of sensor element to optical path length difference becomes possible. Such a calibration is always associated with additional effort.
- FIG. 6 shows a spectrum which was measured with a commercially available OEM spectrometer.
- the spectrometer had a resolution of 2.9nm..3.3nm FWHM (wavelength dependent) and a wavelength range of 430nm..730nm.
- a line sensor element 7 in the spectrometer 6 a CMOS array with 512 sensor elements (pixels) was used.
- the measurement setup corresponded to the illustration in FIG. 5.
- a white LED was used as the light source 2.
- As measuring sensor 5 a preferred membrane-based Fabry-Perot pressure measuring sensor was used. The measuring time resp. Integration time of the sensor element was 1 ms.
- FIG. 7a shows an enlarged section of FIG. 7 in the region of an amplitude extreme value (Uxtremai) with the associated calculated value for an optical path length difference (dGap).
- the intensity values l (d) of the interferogram were calculated in the present preferred example, for optical path length differences (d) of 20 .mu.m to 60 .mu.m. These optical path length differences correspond to geometrical gel distances (d geo ) of 10 ⁇ m to 30 ⁇ m, since the sensor with air (refractive index n - 1) was filled.
- the calculated interferogram as shown in FIGS.
- the measuring cell 5 is formed as a temperature measuring cell in which a temperature-sensitive element 18 is provided which varies depending on the temperature of the optical path length difference (d gap ) of the cavity 11 or varies, as shown schematically as an example in Figure 9.
- the change in the optical path length difference (dc a p) of the cavity 11 can be produced, for example, by a change in a material extent of a temperature-sensitive material, such movement or stretching preferably with at least one of the mirrors 19, 19 ', which may also be partially transparent is coupled, that the distance between the mirrors 19 and 19 'changes in dependence on the temperature.
- the temperature-dependent material 18 itself forms the cavity 11 and has at its surface on both sides and spaced by the material 18 reflecting surfaces 19, 19 'between which at least a portion of the injected light is reflected back and forth.
- the material 18 changes its thickness and thus the mirror spacing d geo, and as a result, after the evaluation according to the present invention, there will be an output signal which corresponds to the temperature applied to the measuring cell 5.
- mount a temperature-sensitive material 18 also adjacent and / or outside the cavity 11, such that, for example, only one of the mirrors 19, 19 'is moved by the stretching of the material 18. In this case, it must simply be ensured that the strain movement of the material 18 is transmitted to at least one of the mirrors 19, 19 'such that the mirror spacing d geo changes accordingly.
- the optical path length difference (dGap) of the cavity 11 can also be changed by changing the refractive index in the path of the light, for example by mechanical and / or thermal stress Material whose refractive power is changed and this interacts with the injected light.
- the change of the optical path length difference (d Ga p) of the cavity 11 can also be formed by a combination of the change of the expansion and the change of the refractive power.
- the measuring cell 5 with the cavity 11 is formed as a pressure measuring cell by a pressure-sensitive element is provided, which changes by a pressure-dependent deformation, such as an elongation, the optical path length difference (dc a p) of the cavity 11 as a function of pressure.
- a pressure-sensitive element is preferably a membrane 14, which is arranged at one end of the cavity 11 and correspondingly strongly bends as a function of pressure and thus changes the optical path length difference (do a p) by changing the geometric path length accordingly.
- the design of the pressure measuring cell 5 as a vacuum pressure measuring cell wherein the pressure-sensitive element preferably has a membrane 14 which is disposed at one end of the cavity 11 and closes there vacuum-tight.
- the membrane 14 is in this case sealingly arranged between a first housing body 15 and a second housing body 15 'at the edge.
- the housing body 15, 15 ' are plate-shaped and made of ceramic material, such as alumina and / or sapphire.
- the housing bodies 15, 15 ' are spaced apart from the membrane 14, so that on both sides of the membrane 14 depending creates a gap-shaped space.
- the gap-shaped space between the first housing body 15 and the membrane 14 is evacuated and forms a reference vacuum chamber 11 and cavity 11 at the same time.
- the light is guided by the optical waveguide 4 to the first housing body 15 and for example via a lens 17 and via a window 16 coupled into the cavity 11.
- the window 16 may be sealingly disposed as a separate part in a recess of the first housing body 15 and / or the entire first housing body 15 may be made of translucent material, such as sapphire.
- the surfaces of the window 16 and of the membrane 14 are designed as mirrors 19, 19 ', whereby at least the mirror on the coupling-in side is designed to be partially reflecting. With suitable surface quality, these surfaces can be used directly as mirror surfaces, but they can also be coated in a known manner.
- the second gap-shaped space on the other side of the membrane which is delimited by the second housing body 15 ', forms the measuring vacuum space which via an opening in the second housing body 15' and via connecting means for the measuring cell 5 with the media to be measured, for example a vacuum process plant. communicated.
- the present invention has the following advantages: The invention makes it possible to use much simpler (smaller
- the method according to the invention is considerably simpler in comparison to the correlation methods according to the prior art and can therefore be implemented very simply and thus correspondingly robust and therefore also requires less computing time, which in turn allows shorter measuring cycles
- the method according to the invention directly supplies the absolute sought measured value and therefore does not require any reference spectra or those for their purpose
- the method according to the invention makes it possible to construct Fabry-Perot sensors whose cavity no longer needs to be coated (for the purpose of improving the contrast or the signal-to-noise ratio) and can therefore be manufactured more simply and cheaply.
- the field of application of such sensors can be shifted to higher temperatures because such coatings, which are no longer necessary, typically determine the maximum service temperature.
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Spectrometry And Color Measurement (AREA)
- Instruments For Measurement Of Length By Optical Means (AREA)
- Optical Transform (AREA)
- Measuring Fluid Pressure (AREA)
- Length Measuring Devices By Optical Means (AREA)
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2010547931A JP5222961B2 (ja) | 2008-02-28 | 2009-02-05 | 干渉式の測定量を評価する方法および装置 |
DE112009000078T DE112009000078A5 (de) | 2008-02-28 | 2009-02-05 | Verfahren und Vorrichtung zur Auswertung einer interferometrischen Messgröße |
CA2713914A CA2713914A1 (en) | 2008-02-28 | 2009-02-05 | Method for evaluating a measured parameter |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CH294/08 | 2008-02-28 | ||
CH2942008 | 2008-02-28 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2009105904A1 true WO2009105904A1 (de) | 2009-09-03 |
Family
ID=39381937
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/CH2009/000044 WO2009105904A1 (de) | 2008-02-28 | 2009-02-05 | Verfahren und vorrichtung zur auswertung einer interferometrischen messgrösse |
Country Status (6)
Country | Link |
---|---|
US (1) | US7728984B2 (de) |
JP (1) | JP5222961B2 (de) |
CA (1) | CA2713914A1 (de) |
DE (1) | DE112009000078A5 (de) |
TW (1) | TWI452271B (de) |
WO (1) | WO2009105904A1 (de) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
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DE102009027592A1 (de) * | 2009-07-09 | 2011-05-12 | Endress + Hauser Gmbh + Co. Kg | Drucksensor mit interferometrischem Wandler und Druckmessgerät mit einem solchen Drucksensor |
JP2012088274A (ja) * | 2010-10-22 | 2012-05-10 | Mitsutoyo Corp | 変位測定装置 |
JP2013510315A (ja) * | 2009-11-05 | 2013-03-21 | クォルコム・メムズ・テクノロジーズ・インコーポレーテッド | 高性能デバイスパッケージにおける環境状態の検出および測定のための方法およびデバイス |
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JP5805498B2 (ja) * | 2011-06-24 | 2015-11-04 | 東京エレクトロン株式会社 | 温度計測システム、基板処理装置及び温度計測方法 |
JP2013007665A (ja) * | 2011-06-24 | 2013-01-10 | Tokyo Electron Ltd | 温度計測装置、基板処理装置及び温度計測方法 |
US9046417B2 (en) * | 2011-06-24 | 2015-06-02 | Tokyo Electron Limited | Temperature measuring system, substrate processing apparatus and temperature measuring method |
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WO2016067268A1 (en) * | 2014-10-30 | 2016-05-06 | Swat Arkadiusz | Method, system and subsystem for interferometrically determining radius of curvature |
WO2016185050A1 (en) * | 2015-05-21 | 2016-11-24 | University Of Limerick | A temperature sensor |
NL2017595A (en) * | 2015-11-10 | 2017-05-26 | Asml Netherlands Bv | Proximity sensor, lithographic apparatus and device manufacturing method |
CN107192449B (zh) * | 2017-04-25 | 2019-04-19 | 哈尔滨工程大学 | 基于法布里珀罗腔干涉测量脉冲激光能量传感器及脉冲光能量测量方法 |
CN114424039A (zh) * | 2019-09-20 | 2022-04-29 | 英福康有限公司 | 确定压力的方法和压力传感器 |
CN112985477A (zh) * | 2019-11-29 | 2021-06-18 | 梅吉特股份有限公司 | 用于在恶劣环境中测量物理参数的光学传感器及其制造和使用方法 |
CN115427766A (zh) * | 2020-04-20 | 2022-12-02 | 北京佰为深科技发展有限公司 | 法珀传感器腔长解调系统和法珀传感器腔长解调方法 |
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- 2009-02-05 DE DE112009000078T patent/DE112009000078A5/de not_active Withdrawn
- 2009-02-05 JP JP2010547931A patent/JP5222961B2/ja not_active Expired - Fee Related
- 2009-02-05 WO PCT/CH2009/000044 patent/WO2009105904A1/de active Application Filing
- 2009-02-26 TW TW098106070A patent/TWI452271B/zh active
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Cited By (3)
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DE102009027592A1 (de) * | 2009-07-09 | 2011-05-12 | Endress + Hauser Gmbh + Co. Kg | Drucksensor mit interferometrischem Wandler und Druckmessgerät mit einem solchen Drucksensor |
JP2013510315A (ja) * | 2009-11-05 | 2013-03-21 | クォルコム・メムズ・テクノロジーズ・インコーポレーテッド | 高性能デバイスパッケージにおける環境状態の検出および測定のための方法およびデバイス |
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Also Published As
Publication number | Publication date |
---|---|
TWI452271B (zh) | 2014-09-11 |
TW200938819A (en) | 2009-09-16 |
CA2713914A1 (en) | 2009-09-03 |
JP2011515659A (ja) | 2011-05-19 |
JP5222961B2 (ja) | 2013-06-26 |
DE112009000078A5 (de) | 2010-12-30 |
US20090219542A1 (en) | 2009-09-03 |
US7728984B2 (en) | 2010-06-01 |
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