WO2008067938A1 - Procédé de mesure de la biréfringence et/ou du retard, en particulier sur des feuilles au moins partiellement transparentes et dispositif associé - Google Patents

Procédé de mesure de la biréfringence et/ou du retard, en particulier sur des feuilles au moins partiellement transparentes et dispositif associé Download PDF

Info

Publication number
WO2008067938A1
WO2008067938A1 PCT/EP2007/010330 EP2007010330W WO2008067938A1 WO 2008067938 A1 WO2008067938 A1 WO 2008067938A1 EP 2007010330 W EP2007010330 W EP 2007010330W WO 2008067938 A1 WO2008067938 A1 WO 2008067938A1
Authority
WO
WIPO (PCT)
Prior art keywords
wavelength
light beams
analyzer
sample
light
Prior art date
Application number
PCT/EP2007/010330
Other languages
German (de)
English (en)
Inventor
Wolfram Aumeier
Original Assignee
Brückner Maschinenbau GmbH & Co. KG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Brückner Maschinenbau GmbH & Co. KG filed Critical Brückner Maschinenbau GmbH & Co. KG
Publication of WO2008067938A1 publication Critical patent/WO2008067938A1/fr

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/8422—Investigating thin films, e.g. matrix isolation method
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/21—Polarisation-affecting properties
    • G01N21/23—Bi-refringence
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/86—Investigating moving sheets

Definitions

  • the invention relates to a method for measuring the birefringence and / or the retardation, in particular at least partially transparent films according to the preamble of claim 1 and an associated apparatus according to the preamble of claim 27.
  • a corresponding measuring method or a corresponding device is primarily used for the fast interference-insensitive real-time measurement of samples by means of electromagnetic radiation, i. in particular radiation in the visible range.
  • the field of application of the invention is therefore not limited.
  • One of the possible applications preferred in the context of the present invention relates to the online measurement (real-time measurement) of the double-billing or the retardation of transparent or at least partially transparent, ie optical plastic films and films during the production process.
  • a quality or process control for example in the production of plastic films, can be carried out online.
  • the measured values are used to calibrate specific film properties and process settings.
  • the costs can be saved by complex offline measurements or misalignments.
  • a partial aspect of the device is u.a. in that during the production process, the film properties can be adjusted in a targeted manner by changing the process and in particular the stretching parameters by means of the measured birefringence properties.
  • the retardation properties of e.g. optical films are adjusted by changing the stretching parameters targeted.
  • the final film property can be adjusted during the production process. The same applies to the adjustment of the process parameters and final film properties, e.g. for shrink films or the minimization of the so-called bowing behavior u.a.
  • a corresponding film thickness measurement in the online or real-time method which can take place externally but can also be an integral part of the claimed measuring device, thus serves to calculate the birefringence values.
  • Birefringence in electromagnetic waves, ie particular in the visible range of light rays, means that a polarized light beam is split into two components and passes through the medium to be examined at different speeds through the film.
  • the birefringence is a value inherent to the material of the sample under investigation or its inherent size, which allows conclusions to be drawn about the material properties of the sample to be investigated. It is often spoken of "retardation”.
  • the two normal and extraordinary beam polarization components pass through the sample to be examined (for example, the film to be examined) at a different speed, namely along a so-called “fast axis” and a so-called “slow axis", which according to the " slow axis "extending polarized light beam quasi” delayed "passes through the sample to be examined, so here is experiencing a" retardation ".
  • the magnitude of the "retardation” is a measure of length, usually in the nanometer range "nm".
  • retardation is often used and understood as an equivalent term to "birefringence", since the retardation corresponds to the birefringence value multiplied by the thickness of the specimen.
  • the measurement of the retardation or birefringence is usually based on the so-called “Senarmont method", in which the phase angle of the polarized light beams is obtained by time-resolved rotation of one of the polarization components.
  • These methods require at least one rotation by a value ⁇ of a polarization component and are therefore for on-line or real-time measurement -A -
  • Senarmont methods have been developed and proposed in which the polarization optics; be replaced by fast-rotating electro- or mechanical-optical elements, so as to enable a timely measurement of retardation or birefringence.
  • Such processes have become known, for example, from WO 99/42796 A1 and within the scope of a further development based thereon from WO 03/040671 A1.
  • the refractive index is known to be the refraction of the electromagnetic wave in The sample to be examined (film), ie the change in direction of the wave due to a local change in its propagation velocity, which is sometimes referred to as "refractive index", which is important in all three spatial axes.
  • US Pat. No. 5,864,403 A for measuring the absolute biaxial refraction values of a plastic material proposes using a white light source with a different wave spectrum, by means of which two light beams are irradiated onto a sample which passes through the sample at the same position both light beams are aligned at a different angle to each other.
  • the beams first pass through polarizers before they hit the sample at the same point.
  • the beams strike another polarizer before hitting a detector after wavelength separation by a spectrograph to measure the beam intensity as a function of wavelength for the angles of incidence of the two beams at different times. From this, the birefringence value or the retardation is ultimately determined.
  • the in-plane value and the out-of-plane value (IP OP value) for the wavelength range should then be calculated according to this prior publication.
  • One way of estimating the retardation or birefringence values online (ie in real time) for fast-moving for- To measure the railway, is to convert the time-resolved signal from the rotating polarization component in a spatially separated polarization information.
  • a polarization-maintaining diffractive optical element ie a diffraction structure
  • Each of these pattern areas is then assigned a single analyzer and a detection unit, wherein the individual analyzers are arranged with respect to their polarization plane in different directions to each other, as can be seen from the prior publication DE 195 37 706 Al.
  • the light beam to be analyzed is multiplied by means of a synthetically generated two-dimensional diffraction structure in a large number of sub-beams same beam profile and the same intensity, the plurality of beams then a corresponding number of linearpolari- sations administraten elements with different angular directions through, then to a ent - Meet a number of detectors whose signals can be Fourieranalysiert with respect to the angle.
  • the object of the present invention is to provide an improved measuring method and an improved apparatus for a real-time birefringence measurement, with which the values that are to be examined are as accurate as possible on-line (that is, in the real-time method) with comparatively little equipment complexity and high resolution Sample, in particular with respect to fast moving foil webs can be determined.
  • the quality and, above all, the process control for example in the production of plastic films and films, which are transparent or partially transparent, can be improved in real time, ie online.
  • the measured values obtained can be used for the calibration of specific film properties and for process engineering settings.
  • the costs are saved by complex online measurements and mishaps.
  • process control here is the targeted influencing of the final film properties by means of the measurement of birefringence (DB) values.
  • the retardation and the birefringence values can be determined on rapidly moving plastic film webs, which are moved, for example, at a speed of up to 600 m / min.
  • the following results can be determined within the scope of the invention:
  • the thickness of the sample (film) can be determined, which can then be used to determine the birefringence values
  • the refractive values can be determined.
  • the corresponding refractive values exist in the thickness direction of the test sample, that is, for example, in thickness direction of the to be investigated film which briefly as out-of-plane birefringence values (n z -n x), (n z -n ⁇ ) denotes advertising the , where the term "out-of-plane” is abbreviated hereafter also abbreviated as "OP". Since these are optical films, of course, the birefringence values in the visible range (from, for example, 400 to 700 nm) of particular interest.
  • the so-called out-of-plane birefringence values are greater than the in-plane birefringence values.
  • the optical films are usually only zeroth or first order (R ⁇ , R ⁇ 2 ⁇ ) is used.
  • birefringence values of higher order generally occur which can not be determined with standard measuring devices. In the case of these devices, order leaps occur which nullify a clear interpretation of the measurement.
  • a remedy here can only be provided by superimposing at least a second measuring beam with a slightly different wavelength collinearly with the main beam. Due to the resulting path differences at different wavelengths, the order of the birefringent foil can then be deduced with the aid of a minimization procedure. For example, e.g. Also, the measurement of previously unclear determinable high-stretched polypropylene films (PP films) possible.
  • PP films polypropylene films
  • FIG. 1 shows a schematic arrangement of a measuring device according to the invention for carrying out the measuring method according to the invention
  • FIG. 2 shows a first embodiment variant for illustrating a possible beam coupling for the in-plane and the out-of-plane excitation
  • FIG. 3 shows an embodiment deviating from FIG. 2 according to a second variant for in-plane and out-of-plane excitation, in particular for optical films;
  • FIG. 4 a schematic representation of a detection unit for detecting the incident light beam with respect to the in-plane or the out-of-plane light beam evaluation;
  • FIG. 5 is an illustration of the light beam split into a plurality of partial beams to produce a different one Intensity distribution after passing through a polarization-dependent analyzer configuration according to a prior art embodiment
  • FIG. 6 shows a corresponding illustration according to FIG. 5, however, for carrying out a measuring method according to the invention
  • FIG. 7 shows a first schematic illustration of a diffraction pattern of a light beam obtained in the context of the measuring method according to the invention, after the light beam has passed through a wavelength-dependent diffractive element generating a multiplicity of partial beams;
  • FIG. 8 shows an exemplary embodiment, deviating from FIG. 7, of a different analyzer arrangement with a correspondingly differently obtained diffraction structure pattern
  • FIG. 9 shows a diagram for explaining the determination of the phase angle and thus the retardation of the birefringent medium in accordance with the examined sample.
  • FIG. 1 a basic schematic representation of an in-plane and an out-of-plane measurement by means of two light beams is explained.
  • a fast-moving transparent or at least partially transparent (optical) plastic film 3 is shown transversely to the film plane.
  • two light beam generating means 5a and 5b are provided, wherein by means of the light beam generating means 5a a falling perpendicular to the plane of the sample to be examined 3 light beam and by means of the light beam generating means 5b an angularly aligned second light beam is generated , the X (or in a closely as possible circumscribed same sample area X) at the same location in a different from 90 ° angle of, for example, ⁇ op incident on the plane of the sample 3, wherein the angle ⁇ 0P smaller than the polarization reflection angle, Thus, preferably less than 50 °, in particular 30 °.
  • Each of the two light beams LS1 and LS2 is generated by means of a light source LQ1 and LQ2, which may for example consist of a white light source such as a lamp or one or more lasers with fixed or tunable wavelengths.
  • a light source LQ1 and LQ2 which may for example consist of a white light source such as a lamp or one or more lasers with fixed or tunable wavelengths.
  • the light beam thus generated is passed through a wavelength separator WS1 or WS2; this can be a monochromator, an edge filter or an acoustically optically transparent be tuneable filter (AOTF).
  • a wavelength separator WS1 or WS2 this can be a monochromator, an edge filter or an acoustically optically transparent be tuneable filter (AOTF).
  • AOTF acoustically optically transparent be tuneable filter
  • the light beams with respect to the in-plane and with respect to the out-of-plane branch can be optically coupled to each other. This is indicated by means of the coupler Cl or C2 in FIG.
  • This coupling can also be used in optical films (samples 3) with zeroth-order measurements to manage with only one light source.
  • the light source LQ2 and the wavelength separator WS2 omitted.
  • the so-called second light beam in the out-of-plane branch is then supplied by the light source LQ1 and by the wavelength separator WS1 alone.
  • the respective light beam LS1 or LS2 is widened with an expander lens CU1 or CU2, in which case the respective light beam LS1 and LS2 first a polarization optics PO1 and PO2 and retardation plates ( ⁇ / 2). passes through and then radiates through the film 3.
  • the optional optical coupling of the two light sources or light beams can serve the following purposes:
  • At least a second wavelength is necessary (as discussed above for example with respect to the multi-wavelength method), which is collinearly irradiated by the approximately equal sample volume.
  • this can be done by using at least one second light beam with a wavelength offset from the first light beam or by using a light beam having a wavelength range.
  • An analogous procedure is possible for several wavelengths.
  • the light source LQ1 having a wavelength of 635 nm and the second light source LQ2 having a wavelength of, for example, 685 nm are collinearly irradiated in the approximately same sample area X
  • higher orders up to the ninth order may be used the sample to be examined are determined.
  • Such values can thus generally vary between 10 to 100 nm, in particular between 10 to 80 nm or 10 to 60 nm or 10 to 50 nm. As stated, values of about 20 nm to 40 nm are often suitable.
  • two light sources LQ1 and LQ2 are used, the light beams generated above each being supplied to a wavelength separator WS1 or WS2, as explained with reference to FIG.
  • the two light beams LS1 and LS2 generated above are coupled to one another via a beam splitter optics SK1 or SK2.
  • the wavelength of the light source LQ1 can be, for example
  • ⁇ 2 (400 + ⁇ ) - 700 nm
  • Switching devices Sl for the first light beam LSl and the switching device S2 for the second light beam LS2 the possibility to control the light source LQ2 controlled in a wavelength ⁇ l + ⁇ and then to determine the order. This principle works analogously when different discrete laser sources are used instead of a broadband light source.
  • the two light sources LQ1 and LQ2 generate light beams which, after passing through the wavelength separators WS1 and WS2 for the in-plane and out-of-plane beam path in a splitting unit SU1 and SU2 in FIG Rays with the same intensity are split unpolarized.
  • These splitting units SU1 and SU2 can consist, for example, of one non-polarizing broadband beam splitter BS1 and BS2 and one each of a 100% mirror M1 or M2.
  • the splitting units can also be realized by all other suitable measures, for example also in the form of an optical waveguide multiplexer.
  • the light beam LS1 is divided via the beam splitter BS1 into the passing light beam LS1_1 and into the light beam LS1_2 branching off from it.
  • the second light beam LS2 is split into the light beam LS2_1 and L2_2 via the second beam splitter BS2.
  • the light beam LS1_1 radiating with the wavelength X 1 is fed to a collimation unit CU1_1 (widening optics CU1_1) and the second part beam LS1_2 to the widening optics CU1_2, thereby widened and subsequently fed to a further beam splitter BS1_1 or BS2_1.
  • a portion of the light beam LS1_1 or LS1_2 emitting with the wavelength X 1 passes through the beam splitter BS1_1 or BS2_1.
  • the second light beam LS2 which is split into two light beams LS2_1 and LS2_2 via the splitting unit SU2 mentioned above, the one light beam LS2_1 likewise being fed to the mentioned beam splitter BS1_1 via an expander optic CU2_1 and the second beam splitter LS2_2 to the further beam splitter BS2_1 a portion of the light beam is deflected parallel to the respective other light beam LS1_1 or LS1_2, so that both on the in-plane branch and on the out-of-plane branch portions of both light beams LS1 or LS2 spread.
  • ⁇ / 2 (often realized in the form of a so-called retardation plate with effecting a ⁇ / 2 phase shift), to then the mentioned polarization optics POl or PO2 and then then the sample 3, for example in the form of a transparent To film.
  • the light beams with the wavelength X 1 and ⁇ 2 each have half the intensity.
  • each of the two split light beams in the two other beam splitters BS1_1 and BS2_1 partially reflected in a 90 ° angle, so that this beam portion with Detectors DETl or DET2 can be used to determine the transmission as a reference.
  • Detectors DETl or DET2 can be used to determine the transmission as a reference.
  • These measurements can also be used to determine the film thickness over the Lambert-Beersche law.
  • switches S1 and S2 (which are arranged in front of the widening optics CU1_2 and CU2_1) serve, as mentioned, for determining the order, but also for calibrating the respective retardation at different wavelengths.
  • FIG. 3 shows a variant embodiment in deviation from FIG.
  • the embodiment according to FIG. 3 is used in particular for the simultaneous determination of the retardation values for optical films in the visible wavelength range.
  • a light beam having a wavelength range X 1 X is thus generated in the light source LQ 1 and the following wavelength range separator WS 1 and subsequently a beam splitter unit SU with a beam splitter BSl and a mirror Ml arranged offset thereto, whereby the light beam LS1 is split into two light beams LS1_1 and LS1_2.
  • the two beam branches produced in this way are fed to each other in-plane and out-of-plane at different angles, ie the beam is perpendicular to the film and the other at an acute angle.
  • a separate second light source LQ2 and a further wavelength range separator WS2 can alternatively be provided for the second beam path, which is delimited in dashed lines in FIG. In this case, the beam splitter SU would then be omitted.
  • the above-mentioned wavelength range separator WSL thus serves to filter out a certain wavelength range in the X 1 X from the one light source LQL generated light beam and transmitting.
  • two light sources LQL and LQ2 used each having a downstream wavelength band separator WSL or WS2 may be that a certain wavelength range X 1 X or X 2 X produced from the in the two light sources LQL and LQ2 filter out light beams and to transmit, wherein X 1 X 2 X and X is the same wavelength ranges, at least overlapping wavelength ranges or can represent mutually offset wavelength ranges.
  • X 1 X 2 X and X is the same wavelength ranges, at least overlapping wavelength ranges or can represent mutually offset wavelength ranges.
  • discrete wavelengths are used instead of a wavelength range.
  • wavelength ranges X 1 X discrete wavelengths X n can also be set, as in the exemplary embodiment according to FIG.
  • Wavelength separators WSl and WS2 (for light beam selection) used for calibration.
  • a monochromator or various edge filters can be used for calibration.
  • the calibrator may be removed or continue to serve as a wavelength range selection unit.
  • the remaining units and their functionality basically correspond to the construction according to FIG. 2, wherein in each wave the beam of light LS1_1 radiating in a wavelength range passes through a beam splitter BS1_1 or BS2_1, as well as the polarization optics, in order then to the sample to be examined, for example in shape of the movie to fall.
  • These measured quantities in the transmitting and receiving part can be used to determine the transmission and for direct determination the film thickness be used over the Lambert-Beersche law.
  • the thickness measurement then serves to calculate the birefringence values via the phase angle or the retardation.
  • the detection units 9 (namely the detection unit 9a for determining the IP values and the detection unit 9b for determining the operating theater values) are explained in more detail below with reference to FIG. 4, as can already be seen from the principle of FIG. With reference to Figure 4, this structure is shown in greater detail, being preceded that the detection units as well as the light beam generating devices in the in-plane and in the out-of-plane beam path are constructed analogously, which is why with reference to Figure 4 only Detection part for the IP or the OP components is described, this detection part 9, 9a for the in-plane branch and in another embodiment as a detection part 9, 9b for the out-of-Plane branch is used (said Detection parts 9, 9a hereinafter also partially referred to as D 1 and D 2 ).
  • the light beam LS either from the in-plane or the out-of-plane branch emerging from the sample and subsequently referred to briefly as LS is elliptically polarized and contains after passing through the sample 3 (in the form of the transparent or partially transparent film 3) after passing through the film 3, the required polarization information in the form of a phase angle, which can be converted into a corresponding value for the retardation and for the birefringence.
  • the light beam in the in-plane as well as in the out-of-plane beam consists of the superimposition of the respectively emitted wavelengths, ie of either the discrete wavelengths irradiated and / or the at least one wavelength range.
  • the light wave beam LS strikes a splitting unit SPLIT in which both the light beam in the in-plane and in the out-of-plane branch is detected by means of a Beam splitter D-BSl is split into a detection light beam D-LSl and D-LS2.
  • the partial beam D-LS1 is fed to a separator D-SEP1 and the further light beam D-LS2 is fed to a second separator D-SEP2.
  • the light beam emerging from the two separators D-SEPl or D-SEP2 is then split into a spatial pattern as a function of the wavelength ⁇ and transferred to a diffractive element DOE (DOE1 or DOE2), which will be explained in detail later a lens Ll or L2 to an analyzer element A arranged thereafter, which in the exemplary embodiment shown comprises an analyzer element Al with respect to one sub-beam D-LS1 and an analyzer element A2 with respect to the second sub-beam D-LS2.
  • Information about the phase angle, the order, etc. of the light beam can be obtained from this image pattern - which will be explained below - with the spatial and intensity information and possibly the color (wavelength) information being determined by means of a downstream camera DETl or DET2 can be recorded and used in a computer.
  • splitting unit SPLIT ultimately serves to achieve a further improved resolution by the splitting.
  • This unit (SPLIT) is shown on the one hand in FIG. 4 using the unit Shift shown there, around which the second detection unit D 2 is formed in a punctiform manner.
  • the "Shift 1" unit also again constitutes a delay element (for example in the form of a retarder plate), for example producing a ⁇ / 4 or ⁇ / 2 or similar phase shift in the branched light beam, thus providing better separation between slower and faster components in the incident light beam LS allows becomes .
  • a delay element for example in the form of a retarder plate
  • a so-called shift unit is arranged between the coupled-out light beam D-LS1 and D-LS2, ie between the beam splitter D-BS1, which is permeable to the first light beam D-LS1 and one Partial beam decouples, which then after passing through the shift unit to the mirror RT, Ml falls and in the illustrated embodiment is deflected accordingly and thereby passes through the other wavelength separator or edge filter (in particular edge filter) D-SEP2.
  • SPLIT IP SPLIT IP
  • SPLIT OP SPLIT OP
  • further detection branches D 1 to D N are coupled via beam splitter BS, as indicated in FIG. 4 by the dotted outline. If, for example, one wants to detect the entire visible region with the highest resolution, for example, only a partial region of the spectrum can be radiated onto the respective diffractive element DOE and detected via an edge filter D-SEP.
  • the respective separator D-sepl or D-SEP2 is, for example for a certain wavelength X 1, X 2, etc. throughout to ⁇ N or a wavelength range A 1 X, but blocking for a different wavelength range A 1 X + ⁇ X.
  • this procedure is exactly reversed. Thus, it is possible to separate the respective excitation wavelengths and ranges.
  • a partial beam is transmitted, which then falls on the detector unit DT3, that is, a detection unit, which, as stated, is required for determining the transmission and the thickness of the film.
  • the detection units will be described below in more detail with reference to FIG. 1 and in particular also with reference to FIG. 5 et seq.
  • the detection units 9 i. the detection units 9a and 9b, constructed analogously for the two beam paths in-plane and out-of-plane, which is why only one detection component for a beam branch is described below.
  • these detection units 9 or 9a and 9b comprise the diffractive element DOE, the lens L1 or L2, the analyzer element A1 or A2 and finally the measuring unit or sensors DET1 or DET2 used for the detection, which preferably consist of a camera.
  • the basic components of the detection unit 9 are based on the aforementioned diffractive element DOE and a downstream analyzer unit A.
  • the detection principle is first explained with reference to FIG. 5 with regard to its basic principle of operation with reference to a method known from the prior art.
  • fractal element DOE in a Pope-maintaining diffuser, ie, a predetermined diffraction pattern pattern BM imaged.
  • the light beam LS is split or fanned out into N partial beams by the diffractive element DOE, which form an image in circular areas 15 on an analyzer arrangement A to be discussed below, these circular areas 15 and so that the diffraction pattern BM are symmetrical around a pitch circle.
  • each individual analyzer 19 is rotated with its plane of polarization by 15 ° with respect to the polarization plane of an adjacent individual analyzer.
  • a light beam LS is split by the mentioned diffractive element DOE into N partial beams.
  • the polarization orientations of the individual analyzers are in angles of
  • N 1, 2, 3, ..., N are the natural integers, and N is the number of particle beams and thus the number of individual analyzers corresponds.
  • an intensity pattern BS arises behind the analyzer arrangement, which can be detected, for example, with individual diodes, line arrays or full-area sensors.
  • LCD cells or, for example, CCD cameras, etc. are suitable for this purpose.
  • the spatial structure may be arbitrary.
  • the measuring method for the conversion of a temporal polarization information into a spatial one explained so far is basically known from the above-mentioned prior publication DE 195 37 706 A1.
  • the wavelength-dependent diffractive properties of the diffractive element DOE are used for the simultaneous detection of the polarization properties (retardation) of a plurality of discrete wavelengths and / or at least one wavelength range.
  • analogous patterns ie analog diffraction pattern B, are generated as a function of the wavelength, depending on the design of the diffractive element used DOE Lich are separated or may be spatially separated and are polarization-preserving at each sample location.
  • FIG. 6 shows the principle representation according to the invention of the wavelength selectivity of a diffractive element DOE with an analyzer arrangement using the example of three discrete wavelengths X 1 , ⁇ 2 and X 3 . If, unlike FIG. 6, no analyzers, ie no polarizers, were used, the same image pattern reproduced in FIG. 6 would result, but then the intensities at all image positions would be the same on the respective pitch circles.
  • a diffraction pattern BM is generated whose individual components also all contain the same polarization information for the respective wavelength. If, as explained, an analyzer A with defined but mutually different polarization angles is brought before each individual pattern (in FIG. 5 or 6 the respective circular area 15 at the relevant imaging position 115), then the phase angle of the birefringent medium can be at different wavelengths or wavelength ranges be detected at the same time. So you can capture the polarization properties in a wide wavelength range and at higher orders at the same time.
  • the diffraction pattern BN reproduced in a spatial representation in FIG. 6 is reproduced once again in a planar view in FIG. 7, whereby at each image position 115 (with the circular surfaces 15 in the exemplary embodiment shown). Then, an analyzer A is positioned in the form of a single analyzer 19, which, as explained above, in the embodiment shown has an orientation of the polarization plane deviating by 15 °.
  • a diffraction pattern is reproduced as an example, depending on the diffractive element DOE used.
  • the image function according to FIGS. 6 and 7 shows an image or diffraction pattern for the case in which a light beam having a plurality of discrete wavelengths (which therefore differ from one another) is used for the sample to be examined. If, instead of discrete wavelengths for the sample to be examined, a light beam is used which comprises a wavelength range, the patterns merge into one another, as is reproduced, for example, in FIG. 7 by the oval borders 115 '.
  • FIG. 7 along the double-arrow representation WW, it is indicated which image points are generated as a function of the wavelength change.
  • the discrete polarization imaging points or areas are indicated, ie those areas in which the light beam is imaged at different locations as a function of the polarization.
  • an analyzer arrangement A that has been appropriately matched must therefore also be used or an analyzer arrangement must be designed accordingly. If these are a few discrete wavelengths, an analyzer arrangement A also be produced using discrete analyzer elements 19. At each pattern position, a single analyzer 19 is then attached to the analyzer element at a defined angle, as already described above. Otherwise, an entire analyzer arrangement with corresponding sections and areas must be generated or adapted accordingly, these areas having to have, for example, 115 'for the evaluation of the corresponding polarization information correspondingly aligned polarization areas.
  • FIG. 8 another example is shown with reference to FIG. 8 if another diffractive element DOE is used, which leads to a different image function. Also in this case, one of the individual image position 115 (which in each case consists of a square area in FIG. 8) must be positioned corresponding to analyzer individual elements 19, or else a common analyzer comprising individual structured analyzer sections 19 is used, which are adapted for detection of a particular polarization orientation according to the arrow representation. This is only intended to show that the most varied image positions and arrangement of analyzers are conceivable and possible, depending on the diffractive element DOE used.
  • the analyzer element provided according to the invention is provided in the form of the individual analyzers 19, for which three paths are available: i) it is possible to use discrete single analyzers 19 in the form of single polarizers 19a, as described above,
  • lithographic or holographic Analysa- tor elements lends itself to the use of lithographically or holographically produced polarization grating arrays on.
  • Each pattern element which is arranged in dependence on the DOE pattern, then has a defined polarization position.
  • the analyzer elements are arranged rotated in relation to each other at least in the range from 0 to ⁇ . The more single analyzers arranged in this area, the higher the resolution of the phase angle becomes.
  • each LCD cell having a certain polarization angle can be adjusted.
  • a calibration method therefore, light of a wavelength can be imaged by the diffractive element DOE on the LCD screen.
  • a defined polarization orientation is then impressed on the individual LCD cells and stored in the computer. puts. The so-called calibration procedure is then repeated for any other wavelengths.
  • the detector is wavelength selective. Depending on the wavelength, a defined spatial pattern is formed according to the DOE structure. The pattern scattered by the DOE is polarization-preserving. The spatial structure defines the wavelength.
  • the generated pattern allows the individual analyzer elements to determine the phase angle and thus the retardation of the birefringent medium.
  • the order of birefringence can be determined online and time synchronously.
  • the retardation in a wide wavelength range can be determined online and synchronously.
  • the transmission can additionally be determined for each wavelength, since the irradiated intensity is also measured in each excitation.
  • the thickness of the sample can be determined via the Lambert-Beersche law.
  • the sample to be examined in particular in the form of a film web to be examined, moves forward at 600 m / min, then with a measuring beam diameter of, for example, 10 mm for the light beams, the pole angles could be determined every 10 ms become.
  • averaging over several measuring points is appropriate or necessary.
  • the thickness of the sample can also be determined by the Lambert-Beersche law are determined, which in turn is used to calculate the birefringence values.
  • the thickness information from external measuring devices of the thickness can also be used for this determination.
  • a monochromator or other discrete wavelengths are used for calibration.
  • the location on the analyzer unit and its imaging on the camera, that is to say in the detection device DET1 or DET2 is then determined.
  • Another calibration method is the use of spectral lines of white light sources (spectral lamps). These allow continuous self-calibration during operation.
  • the spectrum of the excitation LSl with the wavelength ⁇ l are continuously passed through with the maximum sampling rate of the detection unit or detection camera DETl.
  • the average intensity of ⁇ 1 is measured by means of the detector DT3 (shown in FIG. 4) and the intensity of ⁇ 2 is accordingly adjusted, which results in a higher signal level at the detectors, which differs from the signal of ⁇ 1 allows.
  • this probing pulse can also be used with a different polarization.

Landscapes

  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Mathematical Physics (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)

Abstract

Le procédé amélioré ainsi que le dispositif amélioré selon l'invention pour la mesure de la biréfringence et/ou du retard sur des échantillons (3) sont caractérisés entre autres par les points suivants : un ensemble rayonnant comprend au moins une source de lumière (LQ1, LQ2) ou au moins deux sources de lumière (LQ1, LQ2) pour produire deux faisceaux lumineux (LS1, LS2; LS1_1, LS1_2; LS2_1, LS2_2), un élément diffractif (DO; DO1, DO2) reçoit la polarisation, et un module de détection (9; 9a, 9b) avec des analyseurs sensibles à la polarisation (A; A1, A2; 19) sert à mesurer l'intensité du modèle de structure de diffraction (BM) produit par les faisceaux partiels.
PCT/EP2007/010330 2006-12-07 2007-11-28 Procédé de mesure de la biréfringence et/ou du retard, en particulier sur des feuilles au moins partiellement transparentes et dispositif associé WO2008067938A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102006057727.2 2006-12-07
DE200610057727 DE102006057727A1 (de) 2006-12-07 2006-12-07 Verfahren zur Messung der Doppelbrechung und/oder der Retardation, insbesondere an zumindest teiltransparenten Folien sowie zugehörige Vorrichtung

Publications (1)

Publication Number Publication Date
WO2008067938A1 true WO2008067938A1 (fr) 2008-06-12

Family

ID=39106136

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2007/010330 WO2008067938A1 (fr) 2006-12-07 2007-11-28 Procédé de mesure de la biréfringence et/ou du retard, en particulier sur des feuilles au moins partiellement transparentes et dispositif associé

Country Status (2)

Country Link
DE (1) DE102006057727A1 (fr)
WO (1) WO2008067938A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102010011864A1 (de) 2010-03-18 2011-09-22 Brückner Maschinenbau GmbH & Co. KG Verfahren zur Online-Ermittlung mechanischer und/oder optischer Eigenschaften einer Kunststofffolie

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4027161A (en) * 1976-04-05 1977-05-31 Industrial Nucleonics Corporation Minimizing wave interference effects on the measurement of thin films having specular surfaces using infrared radiation
DE3106818A1 (de) * 1981-02-24 1982-09-09 Basf Ag, 6700 Ludwigshafen Verfahren zur kontinuierlichen bestimmung mehrachsiger orientierungszustaende von verstreckten folien oder platten
US5864403A (en) * 1998-02-23 1999-01-26 National Research Council Of Canada Method and apparatus for measurement of absolute biaxial birefringence in monolayer and multilayer films, sheets and shapes
EP0917945A2 (fr) * 1997-11-21 1999-05-26 Kalle Pentaplast GmbH Procédé et dispositif pour le réglage en continu de la rétraction d'une feuille amorphe
WO2004023071A1 (fr) * 2002-09-09 2004-03-18 Zygo Corporation Procede d'interferometrie pour mesures d'ellipsometrie, de reflectometrie, et diffusiometrie, y compris, la caracterisation de structures a films minces

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4668086A (en) * 1985-05-20 1987-05-26 Salomon Redner Stress and strain measuring apparatus and method
DE19537706A1 (de) * 1995-10-11 1997-04-17 Lorenz Diener Verfahren und Vorrichtung zur störunempfindlichen analogen Echtzeitpolarimetrie
AU3299399A (en) * 1998-02-20 1999-09-06 Hinds Instruments, Inc. Birefringence measurement system
US5936735A (en) * 1998-03-31 1999-08-10 Eastman Kodak Company Apparatus and method for determining the optical retardation of a material
JP2005509153A (ja) * 2001-10-16 2005-04-07 ハインズ インスツルメンツ インコーポレイテッド 複屈折測定システムの正確な校正

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4027161A (en) * 1976-04-05 1977-05-31 Industrial Nucleonics Corporation Minimizing wave interference effects on the measurement of thin films having specular surfaces using infrared radiation
DE3106818A1 (de) * 1981-02-24 1982-09-09 Basf Ag, 6700 Ludwigshafen Verfahren zur kontinuierlichen bestimmung mehrachsiger orientierungszustaende von verstreckten folien oder platten
EP0917945A2 (fr) * 1997-11-21 1999-05-26 Kalle Pentaplast GmbH Procédé et dispositif pour le réglage en continu de la rétraction d'une feuille amorphe
US5864403A (en) * 1998-02-23 1999-01-26 National Research Council Of Canada Method and apparatus for measurement of absolute biaxial birefringence in monolayer and multilayer films, sheets and shapes
WO2004023071A1 (fr) * 2002-09-09 2004-03-18 Zygo Corporation Procede d'interferometrie pour mesures d'ellipsometrie, de reflectometrie, et diffusiometrie, y compris, la caracterisation de structures a films minces

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102010011864A1 (de) 2010-03-18 2011-09-22 Brückner Maschinenbau GmbH & Co. KG Verfahren zur Online-Ermittlung mechanischer und/oder optischer Eigenschaften einer Kunststofffolie
DE102010011864B4 (de) 2010-03-18 2022-12-22 Brückner Maschinenbau GmbH & Co. KG Verfahren zur Online-Ermittlung mechanischer und/oder optischer Eigenschaften einer Kunststofffolie

Also Published As

Publication number Publication date
DE102006057727A1 (de) 2008-06-12

Similar Documents

Publication Publication Date Title
EP0618439B1 (fr) Dispositif d'imagerie optique pour l'examen de milieux fortement diffusants
DE60209672T2 (de) Auf Flüssigkristallen basierendes polarimetrisches System, Verfahren zu seiner Kalibrierung, und polarimetrisches Messverfahren
DE2025509B2 (de) Interferenzmikroskop
DE10021378A1 (de) Optische Messanordnung mit einem Ellipsometer
DE60220521T2 (de) Doppelbrechungsmessung für wellenlängen im tiefen ultraviolettbereich
DE10154008C1 (de) Verfahren und Anordnung zur spannungsoptischen Analyse von Festkörpern
DE2127483A1 (de) Verfahren zur interferentiellen Messung von Langen, Winkeln, Gangunter schieden oder Geschwindigkeiten
DE112014002748T5 (de) Spektral kodiertes Hoch-Extinktions-Polarisationsmikroskop
EP3056934A1 (fr) Tete de mesure d'un dispositif endoscopique et procede d'inspection et mesure d'un objet
DE102012104874B4 (de) Optisches Messsystem mit Polarisationskompensation, sowie entsprechendes Verfahren
DE1798143A1 (de) Verfahren zur optischen Ellipsometric von Materialproben
EP1507137B1 (fr) Procédé et dispositif pour l'inspection dépendante de la polarisation et pour l'inspection par résolution spatiale d'une surface ou d'une couche
EP0179016A1 (fr) Polarimètre à double faisceaux fonctionnant en temps réel
DE19621512A1 (de) Verfahren und Anordnung zur Auswertung des wellenlängenabhängigen Polarisationszustandes einer Strahlung
WO2013037833A1 (fr) Procédé et dispositif de mesure de la lumière dispersée
DE2338305C3 (de) Verfahren und Vorrichtung zur Ermittlung der linearen Doppelbrechung eines Materials
DE19913049C2 (de) Verfahren und Vorrichtung zur Bestimmung der Geschwindigkeit
WO2008067938A1 (fr) Procédé de mesure de la biréfringence et/ou du retard, en particulier sur des feuilles au moins partiellement transparentes et dispositif associé
WO2017207751A1 (fr) Dispositif de détermination de l'état de polarisation par mesure d'au moins trois paramètres de stokes
DE2453424A1 (de) Tragbares polarisations-analysegeraet
DE3929713C2 (de) Verfahren zur Messung eines optischen Gangunterschiedes an anisotropen transparenten Objekten
DE102008001448A1 (de) Verfahren und Vorrichtung zum Messen mindestens eines Abbildungsfehlers eines optischen Abbildungssystems
DE102004023030B4 (de) Mehrfachstrahlteiler
WO2019175002A1 (fr) Spectromètre par transformation de fourier, procédé servant à fabriquer un spectromètre par transformation de fourier, et procédé servant à représenter un spectre électromagnétique
WO2016124438A1 (fr) Procédé et système pour la détermination d'une différence de trajet optique entre des ondes lumineuses partielles apparaissant dans un objet biréfringent

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 07856295

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 07856295

Country of ref document: EP

Kind code of ref document: A1