DE102005014446A1 - Polarizer, detector unit and optical sensor as well as educational methods - Google Patents

Polarizer, detector unit and optical sensor as well as educational methods

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Publication number
DE102005014446A1
DE102005014446A1 DE102005014446A DE102005014446A DE102005014446A1 DE 102005014446 A1 DE102005014446 A1 DE 102005014446A1 DE 102005014446 A DE102005014446 A DE 102005014446A DE 102005014446 A DE102005014446 A DE 102005014446A DE 102005014446 A1 DE102005014446 A1 DE 102005014446A1
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Prior art keywords
polarizer
micropolarizers
light
detector
type
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DE102005014446A
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German (de)
Inventor
Matthias Dr. Rottenkolber
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NOVAWAVELIGHT 01 GmbH
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NOVAWAVELIGHT 01 GMBH
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Priority to DE102005014446A priority Critical patent/DE102005014446A1/en
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Application status is Withdrawn legal-status Critical

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    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS, OR APPARATUS
    • G02B5/00Optical elements other than lenses
    • G02B5/20Filters
    • G02B5/201Filters in the form of arrays
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01BMEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00Instruments as specified in the subgroups and characterised by the use of optical measuring means
    • G01B9/02Interferometers for determining dimensional properties of, or relations between, measurement objects
    • G01B9/02055Interferometers for determining dimensional properties of, or relations between, measurement objects characterised by error reduction techniques
    • G01B9/02056Passive error reduction, i.e. not varying during measurement, e.g. by constructional details of optics
    • G01B9/02058Passive error reduction, i.e. not varying during measurement, e.g. by constructional details of optics by particular optical compensation or alignment elements, e.g. dispersion compensation
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS, OR APPARATUS
    • G02B5/00Optical elements other than lenses
    • G02B5/30Polarising elements
    • G02B5/3025Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01BMEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B2290/00Aspects of interferometers not specifically covered by any group under G01B9/02
    • G01B2290/70Using polarization in the interferometer

Abstract

The invention relates to a polarizer for polarizing light, in particular light from the visible, ultraviolet or infrared spectrum, with a polarizer passage surface through which the light to be polarized passes. The polarizer comprises a multiplicity of microscopically small micropolarizers, preferably more than 100,000 micropolarizers, the micropolarizers being arranged side by side in the polarizer passage area and polarizing the transmitted light in light bundles of microscopic cross section. Furthermore, the invention relates to a detector unit comprising the polarizer according to the invention, an optical sensor comprising the detector unit according to the invention, and a method for imaging in which the light used for imaging is polarized in light bundles of microscopic cross-section.

Description

  • The Invention relates to a polarizer for polarizing light, in particular from the visible, ultraviolet or infrared Spectrum, with a passage area through which the polarizing Light passes through. The invention further relates to a detector unit for detecting light comprising a polarizer. Furthermore The invention relates to a sensor for interferometric measurement of surface deformations or the three-dimensional structure of surfaces with a detector unit, which includes a polarizer. Furthermore, the invention relates to an interferometric method for imaging.
  • polarizers for polarizing light are previously known. They have a passage area, below Polarizer passage area called, on, passes through the light to be polarized. In particular, polarizers are known from a disk-shaped polarizing Material in which the disc forms the polarizer passage area, and linearly polarize the light passing through the disk. Such polarizers are from photography as a polarizing filter known.
  • The previously known polarizers are also used in previously known sensors for the interferometric measurement of surface deformations and / or the three-dimensional structure of surfaces. Such sensors are for example from the patents US 6,304,330 B1 and US 6,552,808 B2 known. For the purpose of measurement, the test objects to be examined are irradiated with coherent light, in particular laser light, in the previously known sensors. The measurement of the surface structure takes place on the basis of the spatially resolved measurement of the phase position of the object wave, ie the spatial phase distribution of the light emitted by the illuminated object to be measured. In this case, the phase position of the object wave is measured by comparison with a reference wave. Since with the known detectors, such as CCD chips, not the phase but only the intensity of the incident light can be measured, the phase of the object wave must be determined indirectly via intensity measurements. The determination of the phase from intensity measurements can take place, for example, by means of the phase shift method. For this purpose, the phase of the reference wave, preferably in increments of π / 2 or 90 °, is displaced against the object wave and in each case the associated intensity is measured. The phase can be calculated numerically from the measured intensities based on the following equation:
    Figure 00020001
  • In the above equation, I n is the intensity distribution after the nth phase shift, A R is the amplitude of the reference wave, A o is the amplitude of the object wave and φ (x, y) is the searched phase at location (x, y). The above equation represents a system of equations with the unknowns A R , A O and φ (x, y). If the phase of the reference wave is shifted four times by π / 2, the sought phase of the object wave can be measured from the measured equation Determine intensities I n :
    Figure 00030001
  • It is already known, the phase shift with the so-called spatial Phase shift method. In this procedure will be the four phase states not one after the other, but at the same time, but spatially separated generated. The spatial Separation can be done, for example, by a diffractive optical element take place, which decomposes the incident light into four sub-beams. Each of these subbundles is located in the detector plane behind it with a detector, especially a CCD or CMOS chip, collected. Before the partial light bundles up the detector surfaces meet, in the partial light bundles, the reference waves against the Object waves are phase shifted by different multiples of π / 2.
  • This phase shift is achieved by suitable polarization of the light waves. In a first suitable type of polarization, the light is already polarized in the beam path in front of the diffractive element in such a way that the polarization direction of the object wave, when it occurs on the diffractive element, is perpendicular to the polarization direction of the reference wave. In a second suitable polarization type are object Counterclockwise circularly polarized wave and reference wave, for example, by the object wave on the left circular and the reference wave right circular or the object wave right circular and reference wave is left circularly polarized. In the first suitable type of polarization, the light wave striking the diffractive element is a superimposition of the linearly polarized object wave and the linearly polarized reference wave. Between the diffractive element and the detector plane are in the four sub-beams different combinations of prior art linear polarizers and λ / 4-plate (quarter-wave plate), which combine the suitably polarized object and reference wave so that in each of the four sub-beams, the reference wave is phase-shifted by different multiples of π / 2 with respect to the object wave. Thus, the four partial beams represent a superimposition of the object wave with a reference wave shifted by 0 °, 90 ° (π / 2), 180 ° (π) or 270 ° (3π / 2). In this way, four are obtained in the detector plane Images with π / 2 phase shifted reference wave. The four phase-shifted images are formed simultaneously and can be processed into a phase image by using the above-mentioned formula (F2) by electronic signal processing.
  • In the above-described sensor structure, the need for Distribution of the beam by means of a diffractive element as proved disadvantageous. The diffractive element must be adjusted very accurately. This elevated the for the effort required to assemble the sensor. Also does the required precise adjustment of the beam path the sensor very susceptible to interference, so that the optical design of the sensor must meet very high stability requirements. Furthermore have to the frames generated with the four sub-beams under high Data processing technical effort to be merged.
  • task The invention therefore provides an improved polarizer, detector and to suggest sensor, among other things, from the state The known disadvantages of the art are avoided. In particular, should a polarizer, a detector and an optical sensor proposed will be made possible to dispense with the diffractive element, and the one simple and less susceptible to optical interference allow. In addition, it is an object of the invention an improved to propose an interferometric imaging method in particular to the step of beam splitting can be dispensed with by a diffractive element.
  • To In a first aspect of the invention, the object is achieved by a polarizer containing a variety of microscopic micropolarizers having the Mikropolarisatoren in the polarizer passage area side by side are arranged. In this way occurs on the polarizer falling Light through the Mikropolarisatoren through. The Mikropolarisatoren polarize the light passing through the light beam, d. H. in light bundles, whose Cross sectional area through the passage area of the respective micropolarizer, hereinafter referred to as micro-polarizer passage area, is determined. Thus, the micropolarizers polarize the passing one Light in bundles of light of microscopic cross-sectional area.
  • Preferably indicates the polarizer over 100,000 of the microscopic micropolarizers on. Further preferably the number of micropolarizers is over 300,000, and even more preferred over a million. The Mikropolarisatoren together form a macroscopic Polarisatorfläche, through the light passing through mikropolarisatorweise or polarized pixel by pixel. Advantageously, the diameter the micropolarizers by three or more orders of magnitude smaller than the Diameter of the polarizer. In another advantageous embodiment the diameter of the micropolarizers is less than 10 microns. It is particularly advantageous if the size of a micropolarizer formed micropolarizer passage area in the range of the size of the detector pixels a pixel detector, in particular a CCD or CMOS chip, lies. In a special way In this embodiment, a micropolarizer polarizes the impinging one Light in a surface area, the size of the detector pixels in size a pixel detector, in particular a CCD or CMOS chip, equivalent.
  • With the polarizer according to the invention the advantage is achieved that the incoming light in microscopic light bundles, and so that it can be polarized pixel by pixel. Form in this way the micropolarizers have polarizer pixels that are microscopic in size. As a result, it is possible to achieve this on a pixel-shaped image detector, in particular a CCD or CMOS chip, striking light in targeted and defined way pixel-wise polarized. The polarizer according to the invention thus allows each detector pixel of a pixel detector specific to supply polarized light.
  • Preferably among the Mikropolarisatoren polarizers, the light in different Wei polarize. Thus, from the total amount of micropolarizers, it is possible to pick out pairs of micropolarizers which polarize the light in different ways. The different polarization can be, for example, that the light is linearly polarized in different directions. However, the different polarization can also consist in that the incident light, in particular if it is already linearly polarized on arrival, in a different manner, in particular in different directions, is circularly polarized. This preferred embodiment leads to the advantage that polarization states or pixel-wise defined polarization states can be produced.
  • In In a further preferred embodiment, the plurality of micropolarizers Groups of micropolarizers of the same type. The Mikropolarisatoren of the same type are characterized in that they the light in the same Polarize way. Mikropolarisatoren different types or from different groups preferably polarize the light in different ways. It is particularly advantageous if the polarizers of different types in the polarizer passage area in one arranged in regular patterns are. This can create a regular pixel pattern generated by various defined polarization states.
  • In In a further preferred embodiment, the polarizer comprises micropolarizers type A, B, C and D. The micro polarizers type A and B polarize the light is linear, in directions perpendicular to each other stand. The micropolarizers type C and D consist of one Combination of micropolarizers type A or B, respectively a retarding element, wherein the retarding element the relative phase of mutually perpendicular polarization components a light wave shifts.
  • In In a further preferred embodiment, the retarding Elements of micropolarizers type C and D by λ / 4-plate (quarter-wave plate) educated. This can be done in particular by the fact that the Mikropolarisator Type C microparticulator Type A and a downstream λ / 4-plate and micropolarizer of type D from a micropola risator of the type B and a downstream λ / 4 plate formed is. In this embodiment, it is exploited that a λ / 4-plate the Polarization components along its two main optical axes by 90 ° (π / 2) against each other phase-shifts. By suitable combination of the λ / 4 plate with the upstream linear polarizer type A or type B can Therefore, be achieved by the λ / 4 plate object and reference wave by 90 ° (π / 2) against each other be out of phase. The above-described embodiment allows it therefore, the polarizer according to the invention to use as a spatial phase shifter, by means of Mikropolarisatoren of type A, B, C and D from an overlay of linearly and perpendicularly polarized object and reference waves four phase states generated in which the reference wave with respect to the object wave by 0 °, 90 ° (π / 2), 180 ° (n) and 270 ° (3π / 2) out of phase is. Each of the four polarizer types A, B, C and D thus generates one of the different phase angles between object and reference wave.
  • In In another preferred embodiment, the micropolarizers rectangular, preferably square. In this embodiment acts So it is in the Mikropolarisatoren to rectangular or square Polarizer pixels.
  • In In another preferred embodiment, the micropolarizers arranged in a regular array. This arrangement is preferably such that the Mikropolarisatoren a Make pixel field with N columns and M rows of micropolarizers. The rows and columns are preferably perpendicular to each other, so that gives a Cartesian array of micropolarizers. This embodiment has the advantage that the Polarizer to the regular pixel array a pixel detector, in particular to the regular array the pixel of a CCD or CMOS chip, can be adjusted.
  • In In a further preferred embodiment, the polarizer is made of a regular arrangement formed by similar unit cells. At the regular arrangement may again be an array, in particular a Cartesian array, act. The unit cell is characterized by different micro polarizers Type contains. Preferably, all are different in a unit cell Types of micropolarizers easily represented. This can be with a unit cell generates all the different polarization states are due to the different types of micropolarizers can be generated in the variety of Mikropolarisatoren.
  • In a further advantageous embodiment, the polarizer comprises square micropolarizers type A, B, C and D. In each case a micropolarizer type A, B, C and D form a likewise square unit cell. The unit cell thus consists of four equal-sized partial squares, these sub-squares of the micropolarizers type A, B, C and D are formed. Advantageously, the polarizer is formed from a regular arrangement, in particular a regular Cartesian array of these unit cells. In this plurality of unit cells, types A, B, C and D of micropolarizers are always the same. With this embodiment, the advantage is achieved that on the small surface of a unit cell, but still spatially separated, the four, each by π / 2 (90 °) shifted phase states of the superposition of orthogonal polarized object and reference wave can be generated. Therefore, in the small surface area of a unit cell, there are the four phase states with which the spatially resolved phase φ (x, y) can be determined by measuring the intensity via the intensity measurement.
  • In In another advantageous embodiment, the polarizer comprises three different Types of micropolarizers, namely Micropolarizers type F, G and H. Advantageously, the Micropolarizers type F, G and H also in a regular array arranged. Preferably, the polarizers form the type F, G and H a unit cell. More preferred is the polarizer from a regular array formed of such unit cells. The three different polarizers of the type F, G and H. be designed such that the from an overlay of linearly and orthogonally polarized object and reference waves three different phase states or phase positions he can be witnessed. Out of the three phase states measured intensities can then be the spatially resolved Phase φ (x, y) are determined.
  • One Second aspect of the invention relates to a detecting unit for detecting of light with a pixel detector, in particular a CCD or CMOS chip, the pixel detector a variety of light-sensitive Detector pixels has. Advantageously, as a pixel detector a CCD or CMOS chip is used. According to the invention, the detector unit is characterized in that they a polarizer according to the first aspect of the invention. Of the Polarizer is in front of the pixel detector arranged so that the light incident on the pixel detector has previously passed the polarizer Has. Furthermore, the arrangement of Mikropolarisatoren in the passage surface of the Polarisators matched to the arrangement of the detector pixels. This will achieved that the Arrangement of the micropolarizers with the arrangement of the detector pixels corresponds, so that the light passing through certain micropolarizers to certain Detector pixel drops. In this way it is achieved that by certain Mikropolarisatoren passing light or generated by these Mikropolarisatoren polarization states specifically with the associated Detector pixels can be recorded.
  • In an advantageous embodiment of the detector unit form the Pixel detector and the polarizer a one-piece composite. This can be special be achieved in that the Polarizer is applied as a layer on the pixel detector. The The polarizer-forming layer can be used as a single-layer or multi-layer be formed and applied in a coating process. The layer has a microstructure containing the micropolarizers includes.
  • In a further advantageous embodiment of the detector unit the Mikropolarisatoren and the detector pixels designed in such a way and arranged that the through a Mikropolarisator passing light bundle defined detector pixel hits. This ensures that the of this Mikropolarisator outgoing light beam or of this Mikropolarisator generated polarization state targeted with the defined detector pixels can be included. Advantageously, this is done by one Micropolariser passing light beam to exactly one detector pixel, so that this Detector pixel that of the associated Micropolarizer can record generated polarization state. It is advantageous if only one light on a detector pixel from a Mikropolarisator meets, so that the evaluation of the one Polarization state not by light from other micropolarizers disturbed becomes.
  • In a further preferred embodiment of the detector unit the micropolarizers and detector pixels in a regular array arranged, wherein the two arrangements correspond to each other. This can in particular be designed such that the by a micropolariser passing light beam to exactly one detector pixel of the pixel detector hits, and that on this detector pixel no light falls from other micropolarizers.
  • A further improvement of this embodiment can be achieved in that both the pixel detector and the polarizer with N columns and M rows of Mikropolarisatoren or detector pixels are formed. With this improvement, the detector unit can be designed such that the light beam from a micropolariser with the row and column number (N P , M P ) falls on a well-defined detector pixel with the column and row number (N D , M D ) , This configuration makes it possible with the regular arrangement of Mikropolarisatoren polarization states to produce spatially resolved and To record the same with the pixel detector spatially resolved.
  • One Third aspect of the invention relates to a sensor for measuring surface deformations or the three-dimensional structure of surfaces. Such sensors usually become with a coherent Operated light source. In the beam path of such a sensor is split the light wave into a reference wave and an object wave, advantageously such that reference wave and object wave are polarized linearly and perpendicularly to each other. The DUT is irradiated with the object wave and the object to be measured radiated object wave is superimposed again with the reference wave. For the purpose of evaluation, the superimposed object and reference wave recorded with a spatial phase-shifting recording unit. Draws according to the invention the sensor according to the third aspect of the invention thereby that as Recording unit of the sensor, a detector unit after the second Aspect of the invention is used.
  • One Fourth aspect of the invention relates to an interferometric method for imaging, in particular a method for interferometric Measurement of surface deformations and / or the three-dimensional structure of surfaces. at Such method is the measuring object to be imaged with coherent light illuminated. That of the test object radiated light is evaluated interferometrically. In the method according to the invention is the light in the course of the beam path in light beams of microscopic cross-section polarized, d. H. micro polarized. This polarization can be achieved in particular by using a polarizer according to the invention respectively. Preferably, the inventive method using a detector unit according to the invention or a inventive sensor carried out. In the method according to the invention the advantage is achieved that the Light in microscopic light bundles is decomposed, which can be polarized individually defined.
  • An embodiment of the invention is described below with reference to the 1 to 6 explained in detail:
  • 1 : A top view of the polarizer passage surface ( 12 ) of the polarizer according to the invention ( 10 );
  • 2 : An oblique view of the polarizer according to the invention ( 10 ) with a pixel detector ( 110 );
  • 3a : one to the polarizer passage surface ( 12 ) vertical section through the (2M + 1) -th row of the micropolarizer array of the polarizer ( 10 ) with the underlying pixel detector ( 110 );
  • 3b : one to the polarizer passage surface ( 12 ) vertical section through the (2M) -th row of a micropolarizer array according to the invention of the polarizer ( 10 ) with the pixel detector ( 110 );
  • 4a FIG. 2: a schematic representation of a micropolarizer of type A (FIG. 20 );
  • 4b : a schematic representation of a λ / 4 plate ( 44 . 54 );
  • 5 : the beam path in a sensor according to the invention ( 200 ) with a detector unit according to the invention ( 100 );
  • 6 : the beam path in a second embodiment of the sensor according to the invention ( 200 ) with a detector unit according to the invention ( 100 ).
  • 1 shows a plan view of the polarizer passage area 12 a polarizer according to the invention 10 , The polarizer 10 has a variety of microscopic micropolarizers 20 . 30 . 40 . 50 on, their Mikropolarisator-passage surfaces 22 . 32 . 42 . 52 the viewer of the 1 are facing.
  • The polarizer 10 is formed of four different types of micropolarizers, type A micropolarizers 20 , type B 30 , type C 40 and type D 50 , Micro polarizers type A, B, C, D 20 . 30 . 40 . 50 are square and have a side length of about 6 microns. They are arranged in a Cartesian array of M rows and N columns. Odd line numbers (2M + 1) alternate with type B micropolarizers 30 and type A 20 occupied. Even line numbers (2M) are alternating with type C micropolarisers 40 and type D 50 occupied. Odd column numbers (2N + 1) are alternating with type B and C micro polarizers 30 . 40 occupied. Even column numbers (2N) are of Type A and Type D micropolarizers 20 . 50 occupied.
  • The micropolarizers type A, B, C and D 20 . 30 . 40 . 50 thus form a Cartesian array with (M × N) polarizing pixels. One square, each with a type A micro polarizer 20 , Type B 30 , Type C 40 and type D 50 forms a unit cell 14 , The micropolarizer array can therefore also be described as a two-dimensional Cartesian array consisting of (M / 2 × N / 2) uniform unit cells 14 is formed.
  • The micropolarizers type A 20 polarize the light linearly. The polarizers type B 30 polarize the light also linearly, but the polarization direction of the type B polarizers is 30 perpendicular to the polarization direction of the type A polarizers 20 , The polarizers type C 40 or D 50 are by combining the polarizers type A 20 or B 30 with a λ / 4 plate 44 . 54 (Quarter-wavelength plate) formed as a retarder element.
  • 2 shows an oblique view of a polarizer according to the invention 10 with a pixel detector arranged behind it 110 , As a pixel detector 110 For example, a CCD or CMOS chip can be used. The polarizer according to the invention 10 and the pixel detector 110 are components of the detector unit according to the invention 100 , The pixel detector 110 has a polarizer 10 corresponding geometric structure. It also consists of a Cartesian array of detector pixels 120 with M rows and N columns. The polarizer 10 is so in front of the pixel detector 110 arranged that each detector pixel 120 exactly one micropolarizer type A, B, C or D. 20 . 30 . 40 . 50 assigned. This is the size of Mikropolarisatoren 20 . 30 . 40 . 50 such on the size of the detector pixels 120 matched that each detector pixel 120 from exactly one micro-polarizer 20 . 30 . 40 . 50 is covered. So that's on a detector pixel 120 passing light through the micropolariser in front of it 20 . 30 . 40 . 50 polarized in a defined manner and optionally retarded.
  • 3a and 3b show the polarizer passage area 12 vertical sections through the detector unit according to the invention 100 , It shows 3a a section through a line with the micropolarizers type A and B. 20 . 30 and 3b a section through a line with the micro polarizers type C and D. 40 . 50 , It concerns with 3a and 3b in each case by sections of a line of the Mirkopolarisator-array, which repeat in the right and left direction in the same way periodically. In 3a and 3b the light falls in each case from above. In 3a are above the detector pixels 120 of the pixel detector 110 the micropolarizers type A 20 and type B 30 , These are arranged such that on the left detector pixel 120 only light falls, the previously the micropolarizer type B 30 has happened, and on the right detector pixel 120 only light falls, the previously the micropolarizer type A 20 happened. In 3b are located in front of the detector pixels 120 the micropolarizers type C and D 40 . 50 that the underlying detector pixels 120 completely cover each. As a result, only light that previously hit the type C micropolarizer impinges on the left detector pixel 40 has happened, and on the right detector pixel 120 only light, previously the micropolarizer type D 50 happened. The micropolarizers type C and D 40 . 50 are formed by type A micro polarizers 20 and B 30 , each one λ / 4-plate 44 . 54 upstream.
  • As in 3a and 3b shown is the polarizer 10 as a layered structure on the pixel detector 110 applied. The applied layer structure has several layers or layers. In lower layers are the linear polarizers type A and B. 20 . 30 , In layers above it are in every second row of the pixel array, as in 3b shown the λ / 4-plate 44 and 54 , which in combination with the polarizers type A and B 20 . 30 the polarizers type C and D 40 . 50 result.
  • The above-described layer structure with the microscopic polarizer structure according to the invention and also other embodiments of the polarizer according to the invention can be produced, for example, in a coating method in which the desired structure is produced by corresponding microscopically structured exposure of photosensitive substances. Such coating processes are known, inter alia, from semiconductor technology. On a substrate, for example a glass pane, or directly on the cover layer or surface of the pixel detector 110 For example, spin-coating is used to apply an LPP layer (linear photo polymerization layer) with a very small layer thickness, typically 50 to 100 nm. Spin coating is a standard process in semiconductor technology for producing very thin homogeneous layers. The LPP layer is dried and then exposed appropriately with a UV lamp emitting linearly polarized light. The exposure takes place according to a method used in semiconductor technology for the production of semiconductor microstructures. The LPP layer becomes microscopic structured exposed, preferably in several stages. To create the microscopic exposure pattern, a mask is used, which is microscopically structured, and a mask aligner for aligning the mask and substrate with respect to the UV lamp. For the production of in 1 For example, the regions A and C of the applied LPP layer are exposed by means of the mask with linearly polarized UV light, with the right in the 1 for the micropolarizer type A polarization direction shown. In this exposure, areas C and D of the LPP layer remain unexposed. In a second stage, the exposure of the areas B and C of the LPP layer takes place with the mask. The exposure is carried out with linearly polarized UV light with the right in 1 for the micropolarizer type B polarization direction shown. In this exposure, areas A and C of the LPP layer remain unexposed. The change in polarization direction for the second exposure may be accomplished by rotating either the substrate or the lamp in the Mask Aligner. Preferably, the polarization direction with which the regions and A and C are exposed is perpendicular to the polarization direction with which the regions B and C are exposed.
  • in the Connection to it a functional LCP layer (liquid crystal polymer layer) is likewise produced by spin-coating applied, whose layer thickness is about 1 micron. This LCP layer remains unstructured and exposed to unpolarized UV light to form a molecular To produce crosslinking.
  • advantageously, can in a next Step another layer of LPP can be applied by means of multi-level UV exposure in the same way as the first LPP layer is structured.
  • Of the Layer construction produced by the above steps provides a Polarizer structure, in which light in areas A and B in different Direction is linearly polarized. In the areas C and D takes place a polarization corresponding to areas A and B.
  • For the preferred embodiment according to the embodiment, a further layer sequence of LPP and LCP layers is applied in further steps to the regions C and D in 1 to be provided with a retarder layer. The redatter effect is produced by the choice of suitable layer thicknesses and by suitable structured exposure by means of polarized UV light with a suitable mask, whereby the LCP layer is also exposed to polarized light.
  • At the Passing through the retarder layer in areas C and D of Polarizers, the light in the way polarization changed that to each other vertical polarization components out of phase with each other become. In contrast, the light passes through the areas A and B without Retarder polarization unchanged through. If appropriate Layer thickness affects the retarder layer in the areas C and D. as λ / 4-plate, that along the mutually perpendicular polarization components along the main optical axes by 90 ° or by π / 2 against each other phase-shifts.
  • On this way, with the method described above, a polarizer be made with a microstructure consisting of polarizers is formed of the type A, B, C and D. Through the polarizers of Type A and B, the light is polarized linearly and perpendicular to each other. The polarizers of type C and D become the polarization components of the incident light along the main optical axes first m 90 ° or π / 2 against each other out of phase and then polarized in the same way as in the Polarizers type A and B.
  • 4a and 4b serves to illustrate the phase shift between the object and reference waves through the type A, B, C or D polarizers. 4a shows a linear polarizer of type A, whose polarization direction forms an angle θ = 45 ° with the x-axis. Object wave and reference wave meet perpendicular to the plane of the drawing, ie in the z-direction, on the micropolarizer of type A. In this case, the object wave with the searched phase φ is linearly polarized parallel to the x-axis and the reference wave is linearly polarized parallel to the y-axis. After passage of object and reference wave through the polarizer type A is of the underlying detector pixel 120 the intensity I A detected. For the normalized intensity I A then:
    Figure 00170001
  • In a linear polarizer of type B, the polarization direction is perpendicular to the polarization direction of the polarizer of type A. The polarization direction in the case of a type B polarizer therefore includes an angle of θ = 135 ° with the x-axis. The detector pixel located behind a type B polarizer 120 measures the intensity I B. For the normalized intensity I B :
    Figure 00170002
  • The micropolarizers type C and D 40 . 50 are by combining the polarizers type A and B 20 . 30 with a λ / 4 plate 44 . 54 formed, whose retarding properties are exploited for the purpose of phase shifting. In 4b is a λ / 4 plate 44 . 54 shown schematically. A λ / 4 plate has a slow and a fast main axis. A λ / 4 plate 44 . 54 is so thick that the light polarized along the slow major axis passes through the λ / 4 plate 44 is delayed by 90 ° (π / 2) or a multiple thereof relative to the light polarized along the fast major axis. Is a λ / 4 plate, whose fast main axis along the x-axis runs with the in 4a shown type A polarizer 20 combined, this results in a type C polarizer 40 , Behind the type C polarizer 40 becomes with the detector pixel 120 the intensity I C measured. For the normalized intensity I C, the following applies:
    Figure 00180001
  • Will that be in 4b shown λ / 4-plate with a micropolarizer type B 30 combined, whose polarization direction includes an angle θ = 135 ° with the x-axis, we obtain a type D polarizer 50 , Behind a type D polarizer the intensity I D is measured. For the normalized intensity I D, the following applies:
    Figure 00180002
  • In this way, one can measure behind the polarizers of the type A, B, C, D, the intensities I A , I B , I C , I D with the defined phase positions 0, π / 2, π, 3 / 2π. From these intensities, according to the formula F2, the phase φ (x, y) of the unit cell 14 be determined by the incident light. In this way, one obtains a measured value for the phase of the point on the measurement object which corresponds to the respective unit cell.
  • 5 shows a sensor according to the invention 200 with a detector unit according to the invention 100 which in turn is a polarizer according to the invention 10 having. The light source is a laser 210 , In a first beam splitter 212 the light becomes an object wave 220 and a reference wave 222 divided up. With the ob ject wave 220 becomes the measurement object 230 irradiated. The of the test object 230 returned object wave is in the polarizing beam splitter 214 with the reference wave 222 superimposed. Before that, the object wave has the λ / 4 plate 216 a total of twice, whereby the polarization plane of the object wave is rotated by 90 °. In the superposition of object wave 220 and reference wave 222 formed wave 224 are object wave 220 and reference wave 222 therefore polarized linear and perpendicular to each other. This overlay 224 from object wave 220 and reference wave 222 meets the detector unit according to the invention 100 , The detector unit according to the invention 100 is formed by a pixel detector 110 and an upstream polarizer according to the invention 10 , The light impinging on the polarizer is polarized by micropolarization and then by the respective detector pixel behind the micropolarizer 120 detected. For each unit cell of the polarizer, the intensities I A , I B , I C and I P are detected. From these, the phase angle of the light striking the unit cell can be calculated according to the formula F2.
  • 6 shows a sensor according to the invention 200 operating according to another interferometric, shearographic method. At the in 6 shown interferometric sensor 200 becomes the object of measurement 230 reflected coherent light with a polarizing steel divider 218 divided up. The transmitted light falls as an object wave on the detector unit according to the invention 100 , That from the beam splitter 218 laterally split light is between two opposing, by a small angle α tilted against each other mirrors 250 . 252 reflected and then as a reference wave again through the polarizing beam splitter 218 superimposed with the object wave. The thus sheared against itself light strikes the detector unit according to the invention 100 consisting of the pixel detector 110 and the prior inventive polarizer 10 , In the superimposition of the object wave and the reference wave obtained by shear, the object wave and the reference wave are linearly polarized perpendicular to one another. With the detector unit according to the invention intensities I A , I B , I C I D for each unit cell 14 measured, from which the gradient of the phase position of the object wave in the shear direction can be determined.

Claims (18)

  1. Polarizer ( 10 ) for polarizing light, especially light from the visible, ultraviolet or infrared spectrum, with a polarizer passage area ( 12 ) through which the light to be polarized passes, characterized in that the polarizer ( 10 ) a plurality of microscopic micropolarizers ( 20 . 30 . 40 . 50 ), preferably more than 100,000 micropolarizers ( 20 . 30 . 40 . 50 ), the micropolarizers ( 20 . 30 . 40 . 50 ) in the polarizer passage area ( 12 ) are arranged side by side and polarize the passing light in light bundles of microscopic cross section.
  2. Polarizer ( 10 ) according to claim 1, characterized in that the diameter of the micropolarizers ( 20 . 30 . 40 . 50 ) is less than 15 microns, preferably less than 10 microns.
  3. Polarizer ( 10 ) according to any one of the preceding claims, characterized in that the size of a micro-polarizer ( 20 . 30 . 40 . 50 ) Mikropolarisatordurchtrittsfläche ( 22 . 32 . 42 . 52 ) in the range of the size of a detector pixel ( 120 ) of a pixel detector ( 110 ), in particular a CCD or CMOS chip.
  4. Polarizer ( 10 ) according to one of the preceding claims, characterized in that the polarizer ( 10 ) Micropolarizers ( 20 . 30 . 40 . 50 ), which polarize the light in different ways, in particular in different linear directions and / or in different circular directions.
  5. Polarizer ( 10 ) according to one of the preceding claims, characterized in that the plurality of micropolarizers ( 20 . 30 . 40 . 50 ) Comprises groups of micropolarizers of the same type, the micropolarizers of the same type polarizing the light in the same way.
  6. Polarizer according to one of the preceding claims, characterized in that the plurality of micropolarizers ( 20 . 30 . 40 . 50 ) Micropolarizers type A ( 20 ), B ( 30 ), C ( 40 ) and D ( 50 ), the type A micropolarizers ( 20 ) and B ( 30 ) polarize the light linearly, the polarization direction of the micropolarizers type A ( 20 ) orthogonal to the polarization direction of type B micropolarizers ( 30 ) and wherein the micropolarizers type C ( 40 ) and D ( 50 ) from a combination of micropolarizers type A ( 20 ) or B ( 30 ) with a retarding element ( 44 . 54 ), whereby the retarding element ( 44 . 54 ) shifts the relative phase of mutually perpendicular polarization components of a lightwave.
  7. Polarizer ( 10 ) according to the preceding claim, characterized in that the micropolarizers of the type C ( 40 ) and D ( 50 ) of linear polarizers with a downstream λ / 4 plate ( 44 . 54 ), preferably in that the micropolarizers type C ( 40 ) from a micropolarizer type A ( 20 ) and a downstream λ / 4 plate ( 44 ) and the type D micropolarizers ( 50 ) of type B micropolarizers ( 30 ) and a downstream λ / 4 plate ( 54 ) are formed.
  8. Polarizer ( 10 ) according to one of the preceding claims, characterized in that the micropolarizers ( 20 . 30 . 40 . 50 ) are rectangular, preferably square.
  9. Polarizer ( 10 ) according to one of the preceding claims, characterized in that the micropolarizers ( 20 . 30 . 40 . 50 ) are arranged in a regular array, preferably such that the micropolarizers ( 20 . 30 . 40 . 50 ) the polarizer passage area ( 12 ) pixel-like, more preferably such that the Mikropolarisatoren ( 20 . 30 . 40 . 50 ) form a pixel array with M rows and N columns of micropolarizers.
  10. Polarizer ( 10 ) according to one of claims 5 to 9, characterized in that the polarizer ( 10 ) from a regular array of similar unit cells ( 14 ), each unit cell ( 14 ) Micropolarizers ( 20 . 30 . 40 . 50 ) of different types.
  11. Polarizer ( 10 ) according to the preceding claim, characterized in that the polarizer ( 10 ) Type A square micropolarizers ( 20 ), B ( 30 ), C ( 40 ) and D ( 50 ) and that the unit cell ( 14 ) forms a square, which is formed from four equal-sized partial squares, whereby the partial squares of each one micropolarizer of types A ( 20 ), B ( 30 ), C ( 40 ) and D ( 50 ) are formed.
  12. Detector unit ( 100 ) for detecting light with a pixel detector ( 110 ), in particular a CCD or CMOS chip, wherein the pixel detector ( 110 ) a plurality of light-sensitive detector pixels ( 120 ), characterized in that the detector unit ( 100 ) a polarizer ( 10 ) according to any one of claims 1 to 11, wherein the polarizer ( 10 ) in front of the pixel detector ( 110 ) and the arrangement of the micropolarizers ( 20 . 30 . 40 . 50 ) with the arrangement of the detector pixels ( 120 ) corresponds.
  13. Detector unit ( 100 ) according to the preceding claim, characterized in that the polarizer ( 10 ) with the pixel detector ( 110 ) forms an integral composite, in particular in such a way that the polarizer ( 10 ) as a single-layer or multi-layer structure on the pixel detector ( 110 ) is applied.
  14. Detector unit ( 100 ) according to one of the two preceding claims, characterized in that by a Mikropolarisator ( 20 . 30 . 40 . 50 ) passing light beam on defined detector pixels ( 120 ), in particular to exactly one detector pixel ( 120 ), in particular such that a detector pixel ( 120 ) only light from a micro polarizer ( 20 . 30 . 40 . 50 ) meets.
  15. Detector unit ( 100 ) according to one of the three preceding claims with a polarizer ( 10 ) according to one of claims 9 to 11, characterized in that the detector pixels ( 120 ) are arranged in a regular arrangement, the the regular arrangement of Mikropolarisatoren ( 20 . 30 . 40 . 50 ), in particular such that by a micro-polarizer ( 20 . 30 . 40 . 50 ) passing through light beam to exactly one detector pixel ( 120 ) of the pixel detector ( 110 ) and that on this detector pixel ( 120 ) no light from other micropolarisers ( 20 . 30 . 40 . 50 ) falls.
  16. Sensor ( 200 ) for the interferometric measurement of surface deformations and / or the three-dimensional structure of surfaces, which is provided with a coherent light source ( 210 ), the light wave being converted into an object wave ( 220 ) and a reference wave ( 222 ), the measured object ( 230 ) with the object wave ( 220 ) is irradiated, and wherein the object to be measured ( 230 ) radiated object wave ( 220 ) with the reference wave ( 222 ) is superimposed and recorded for evaluation with a recording unit, characterized in that the receiving unit of the sensor is formed by a detector unit ( 100 ) according to any one of claims 12 to 15.
  17. Interferometric method for imaging, in particular method for the interferometric measurement of surface deformations and / or the three-dimensional structure of surfaces, in which the measuring object to be imaged ( 230 ) is illuminated with coherent light, and in which the object to be measured ( 230 ) radiated light is evaluated interferometrically, characterized in that the interferometric evaluation comprises a method step in which the light wave to be evaluated is micro-polarized in light bundles of microscopic cross-section.
  18. Method according to the preceding claim, characterized in that the method step of micro-polarizing using a polarizer ( 10 ) according to one of claims 1 to 11, and / or the imaging using a detector unit ( 100 ) according to one of claims 12 to 15 and / or a sensor ( 200 ) according to claim 16.
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EP1447689A2 (en) * 1997-05-09 2004-08-18 Rolic AG Optical element comprising a structured retarder
US20050046865A1 (en) * 2003-08-28 2005-03-03 Brock Neal J. Pixelated phase-mask interferometer

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EP1447689A2 (en) * 1997-05-09 2004-08-18 Rolic AG Optical element comprising a structured retarder
US20050046865A1 (en) * 2003-08-28 2005-03-03 Brock Neal J. Pixelated phase-mask interferometer

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