WO2018158435A1

WO2018158435A1 - Deflectometer, reference pattern and method for determining the topography of an object

Info

Publication number: WO2018158435A1
Application number: PCT/EP2018/055190
Authority: WO
Inventors: Mathias Ziebarth; Thomas Stephan; Jan Burke
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.; Karlsruher Institut für Technologie
Priority date: 2017-03-02
Filing date: 2018-03-02
Publication date: 2018-09-07
Also published as: DE102017203390B4; DE102017203390A1

Abstract

The invention relates to a deflectometer for determining the topography of an object, having a display, which is designed to reproduce a reference pattern. The reference pattern comprises a first plurality of spirals and a second plurality of spirals, wherein the direction of turn of the first plurality of spirals is opposite to the direction of turn of the second plurality of spirals. The deflectometer is further designed to provide topographic information regarding the object, on the basis of a reflection of the reference pattern on the object.

Description

DEFLECTOMETE, REFERENCE PATTERNS, AND METHOD FOR

TOPOGRAPHIC DETERMINATION OF AN OBJECT

description

Technical area

Embodiments of the present invention relate to topography determination by means of deflectometry.

Background of the invention

Known concepts for surface determination are briefly discussed below. Deflectometry is used, for example, for keratography, ie for determining the surface of the cornea, in particular of the human eye. By way of example, with a conventional device (keratoscope), as shown in FIG. 14, only changes in the slope of the cornea in the radial direction can be measured, thus making it possible to estimate the corneal topography. Although the shown embodiment of a keratoscope may still be sufficient for the estimation of the corneal topography, a much more precise method is required for the measurement of precision optics.

It can be seen in Fig. 14 that a screen, on which reference strips are mounted, has a hemispherical shape. As a result, the stripe pattern reflected on the cornea (which is also approximately spherically shaped) appears to be regular, as shown in FIG. 15. What conventional concepts can not afford is a complete determination of the surface normal since the tangential component can not be measured with the known fringe pattern shown in, for example, FIG.

For the deflektometric measurement of both direction derivatives by displacement of a static pattern, a method has been proposed in [1] which can determine both directions by displacing a crossed Cartesian fringe pattern (ie with straight streaks) in only one spatial direction. The direction is chosen so that the strip throughput speeds are different in the vertical and horizontal directions. Then, by using suitable phase shift formulas (which are nothing more than digital filter windows of very short length (about 5 elements)), a signal frequency selection can be made and the corresponding signal nalphase be determined, from which then the directional derivatives result. For example, in [1], using a static pattern simplifies the problem of lens inspection because UV light can be used to suppress the backside reflection. Frequency selection by phase shifting has been known for some time (see [2]).

The recording of deflectometric data in a polar coordinate system has already been proposed in [3]; However, here the data were obtained by a laser beam scanning on concentric circles and the disadvantage of the scanning method, the long measuring time (about 1 minute) remains. In addition, the angle of acceptance of the deflected beam system is very low, severely limiting the measurable surface shapes.

The predistortion of a Cartesian pattern, which then appears to be regular after reflection on the human cornea, has been described in [4]; however, the temporal shift of the pattern was indeed omitted here and the data was evaluated by loss of spatial resolution by a sideband method.

The measurement of an aspherical, rotationally symmetric mirror was demons- ized in [5], but here a flat LCD screen was used as a pattern generator, which represented concentric circles - the principle is therefore similar to the keratoscope mentioned above.

There is therefore a need for a concept for improved topography determination by means of deflectometry, which for example offers a better compromise with regard to measuring duration and precision.

Summary of the invention

Fig. 16 shows a camera image taken for a cross-pattern deflectometry. The object to be examined is a spectacle lens with a surface of ~ 8.5D. The marker is useful to identify the strip number. As can be seen from reference [1] in Fig. 16, a regular crossed stripe pattern on a curved surface is naturally distorted. Especially towards the edge, the stripes become very dense and weak in contrast. The distortion of the fringe pattern would have to be compensated for by a predistortion of the reference fringe pattern so that the mirrored pattern appears straight again; but this would no longer fit the object surface, as soon as the pattern is shifted laterally (sa [4]). This unnecessarily complicates strip evaluation with conventional concepts.

Some of the inventive concepts described hereinbelow address the particular requirements of metrology of circled areas by already employing the obvious treatment of the problem in polar coordinates in the measurement. The problem with the rotation of a reference screen (namely, no displacement of the pattern in the radial direction) is avoided by skewing the crossed stripes (and thus creating spirals). As a result, as in the Cartesian case, both required directional derivatives can be measured with a reference pattern. By exploiting the existing tangential cyclicity of the recorded image data, further advantages can result, in particular in the data integration for the deflectometry.

Embodiments provide a deflectometer for topography determination of an object. The deflectometer includes a display configured to render a reference pattern, the reference pattern having a first plurality of spirals and having a second plurality of spirals, and wherein a winding direction of the first plurality of spirals is opposite to a winding direction of the second plurality of spirals , Further, the deflectometer is configured to provide topographic information about the object based on a reflection of the reference pattern on the object. The display may be a screen, an area on which the reference pattern is applied, or any other display capable of displaying the reference pattern.

The exemplary embodiment described is based on the idea that a reflection on a surface based on the described reference pattern can be used to particular advantage in order to determine a surface structure / topography of the object. In particular, the mentioned reference pattern offers the advantage that distortions of the spirals, in contrast to circles, can detect distortions of the reference pattern in two directions. The distortions, due to unevenness of a surface of the object from which the reflection is detected, can be evaluated so that a surface structure of the object can be described. Furthermore For example, one spiral, for example the first plurality of spirals, may be used based on spirals with opposite winding direction / orientation / rotation direction to determine a distortion in a first direction and a second spiral, for example the second plurality of spirals to determine a distortion in a second direction. Hereby, based on the distortion in the first direction and the distortion in the second direction, two directions, for example, independent directions, can be described. For example, the directions may be projected on X and Y directions of a Cartesian coordinate system or radial and tangential directions of a polar or cylindrical coordinate system to describe the surface structure. The first plurality of spirals and the second plurality of spirals are further configured to reproduce a periodic intensity pattern in the radial and tangential directions of the display. In the radial direction, the period can also be variable, whereby a periodic or quasi-periodic reference pattern in the radial direction is described by the reference pattern. In summary, the described embodiment, based on the described distortions, can determine local inclinations of the surface of the object and combine them to perform a topography determination of the surface of the object. According to embodiments, the first plurality of spirals and the second plurality of spirals are concentrically arranged such that the first plurality of spirals and the second plurality of spirals have a common center. The arrangement described provides a compact concentric arrangement of the spirals and allows the advantageous use of a common frame of reference.

According to embodiments, distances between spiral arms of the first plurality of spirals and / or the second plurality of spirals remain radially constant. The reference pattern thus described enables a simple construction of the reference pattern from two conventional spirals, for example arithmetic or archival spirals.

According to embodiments, spacings between spiral arms of the first plurality of spirals and / or the second plurality of spirals increase radially. The exemplary embodiment described makes it easy to generate reference patterns that provide predistortion, for example for spherical surfaces of a measurement object. According to embodiments, the spacings between the spiral arms increase in geometric progression, for example according to a geometric sequence. In other words, the radius of such a spiral increases exponentially with a rotation angle of the spiral, according to r = ae ^ktp , where φ is the rotation angle and r is the radius. The described embodiment describes a reference pattern with logarithmic spirals whose radius is subject to exponential growth, the exponent being given by the so-called slope k. Logarithmic spirals are particularly advantageous because reference patterns derived therefrom provide predistortion for spherical surfaces and the spiral arms of the first plurality of spirals and the second plurality of spirals can intersect at a large angle. Due to the large cutting angle, usually 90 °, it is very easy to obtain linearly independent slope components from the reflection. Based on the linearly independent slope components, a topography determination of the object surface can be carried out with simple means.

According to embodiments, spiral arms of the first plurality of spirals and spiral arms of the second plurality of spirals intersect at an angle that is less than 180 ° and greater than 0 ° or less than 100 ° and greater than 80 °. The embodiment described can be used to advantage to provide two possible independent deflection directions, i. Distortion directions to determine what a simple Topografiebestimmung is possible.

According to embodiments, spiral arms of the first plurality of spirals and spiral arms of the second plurality of spirals intersect at an angle of 90 °. By directly perpendicular spiral arms can be determined with simple means directly two linearly independent deflection directions. Based on the linearly independent deflection directions, it is possible to directly deduce linearly independent topography information, thus making it easy to perform a topography determination.

According to embodiments, a first radius of the first plurality of spirals has a greater pitch than a second radius of the second plurality of spirals. The described embodiment offers the possibility of adjustable topographical determination accuracy, with a larger lead resulting in a spiral more suitable for detecting tangential topography change whereas a lower pitch lead is more suitable for detecting radial topography changes. According to embodiments, the display is arranged relative to the object so that a reflection of the reference pattern is produced on a reflective surface of the object. The arrangement described enables a simple mapping of the reference pattern onto a surface of the object.

According to embodiments, the deflectometer includes a camera disposed in a common center of the first plurality of spirals and the second plurality of spirals. Furthermore, the camera is designed to detect a reflection of the reference pattern on the object. The described embodiment can advantageously make possible a compact design for a keratograph or another deflectometric instrument. Furthermore, a cost-effective camera can be used here, which has sufficient spatial resolution, so that the deflectometer can be manufactured with favorable components.

According to embodiments, the deflectometer comprises a camera, for example, laterally offset from the display, or generally arranged so that it can detect a reflection of the reference pattern on the object. The described deflectometer can perform the topography determination by means of a cost-effective camera with sufficient spatial resolution. Furthermore, the arrangement options allow increased flexibility in terms of the design of the deflectometer.

According to exemplary embodiments, the deflectometer is designed to perform a topography determination of a rotationally symmetrical object or of a quasi-rotationally symmetrical object. For example, the described embodiment can advantageously arrange the plurality of spirals within a circle so that their image covers the entire object as a reflection. Thus, the entire object can be detected with the reference pattern with one or a few shots. Incidentally, quasi-rotationally symmetric objects are predominantly rotationally symmetric with small deviations.

According to embodiments, the deflectometer is designed to rotate the reference pattern and the object relative to one another. Furthermore, the deflectometer is designed, based on the rotation, to obtain images of the rejections of the rotated reference pattern. Based on the periodic intensity distribution of the reference pattern, by relative rotation of the reference pattern to the object, the object and thus the Topography of its surface, to be more accurately captured. For example, a camera can be used to detect a reflection sufficiently frequently per revolution. In particular, it is advantageous here if the frequency of picking is selected as a function of one of the multiple numbers of spirals. For example, if the first plurality of spirals 11 has spirals and the second plurality of spirals 9 have spirals, it is advantageous to detect the reflection per revolution at least 23 times in preferably uniformly spaced detection times. In other words, for improved topography determination, a reflection can be detected at least as often per revolution that the sampling rate! per revolution is greater than twice the number of spirals of the larger majority of spirals.

According to embodiments, the deflectometer is configured to rotate the reference pattern on the display. Furthermore, the deflectometer is designed to obtain images of the reflections of the rotated reference pattern based on the rotated reproduction. The described embodiment can advantageously enable a rotated detection without having to move the object. For this purpose, for example, the reference pattern can be played in a rotating manner on a computer screen or a disk on which the reference pattern is applied can be used as a rotating display. This is particularly advantageous in the application as a keratographer, since a patient whose eye can represent the object can not be moved (rotated) for a rotated capture.

According to exemplary embodiments, the deflectometer is designed to perform the topography determination on the basis of phase information. For this purpose, the deflectometer is designed to obtain the phase information based on the images of the reflections of the rotated reference pattern. Due to the periodic structure of the reference pattern, it is easy to determine the expected phase shifts for both inclination directions of the surface in a rotated reference pattern. If, due to unevenness of the surface, the reflection of the reference pattern has distortions, this is reflected by the phase information derived from the reflection. In combination with the expected phase information, it is thus easy to characterize unevenness and consequently to perform a topography determination of the object. In general, the procedure mentioned here with respect to other periodic reference patterns is also referred to as Phase Measuring Deflectometry (phase-measuring deflectometry). According to exemplary embodiments, the deflectometer is designed to obtain the phase information based on a discrete Fourier transformation of the images of the reflections of the rotated reference pattern. Using a discrete Fourier transform, such as the FFT (Fast Fourier Transform), the phase information can be determined quickly and with little computational effort. For this purpose, for example, a Fourier transformation can be applied over a time axis of the recordings. In particular, a pixel on which the reflections of the reference pattern can be viewed can be used to generate a time signal, wherein the time signal describes the rotation of the reference pattern. The time signal can now be transformed into the frequency domain by means of the Fourier transformation in order to obtain a spectrum. Thus, one spectrum can now be generated per pixel, which is evaluated at the frequency which is dependent on the number of the first plurality of spirals or the number of the second plurality of spirals. The phase at said frequency can thus be compared with a comparison phase in order to characterize a distortion by the reflecting surface. In particular, plural numbers of spirals offer advantages whose numbers are prime, for example 9 and 11. Based on the divisiveness, a phase ambiguity of distortion can be resolved, as described in detail in [6], thus more reliably characterizing surface unevenness.

According to embodiments, the number of spirals of the first plurality of spirals is a prime factor of the number of spirals of the second plurality of spirals. Due to the divisiveness, phase ambiguities of phase information can be resolved based on number-theoretical considerations.

According to embodiments, the deflectometer is designed to obtain the phase information based on phase shift formulas from the images of the reflections of the rotated reference pattern. By means of filters, phase information about phase shift formulas can be obtained on the basis of a time signal of the rotated recordings (for example a time signal of one pixel of the recordings). In this case, a small number of recordings and filters with few elements can be sufficient to obtain the phase information.

According to exemplary embodiments, the deflectometer is designed to obtain a first phase information based on recordings of a rotated reproduction of the reference pattern from the first plurality of spirals. Furthermore, the deflectometer is sets to obtain second phase information based on recordings of a rotated reproduction of the reference pattern from the second plurality of spirals. Further, the defectometer is configured to obtain a topography determination based on the first phase information and the second phase information. By determining the first phase information, topography changes along a first direction may be detected separately from topography change along a second direction. A combination can be used to obtain an accurate determination of the topography of the surface of the object. According to exemplary embodiments, the defectometer is designed to determine deflections of beam paths based on the phase information. Further, the defectometer is configured to determine a plurality of pitch parameters of a reflective surface of the object based on the deflections of beam paths. The slope parameters may characterize local changes / slopes in the surface of the object. Furthermore, based on a determination of slope parameters over the entire surface of the object, it is thus easy to determine a topography of the object.

According to exemplary embodiments, the defiectometer is designed to perform the topography determination of the object based on an integration of the plurality of gradient parameters. By integration of the slope parameters, for example based on a given starting point, a surface of the object can be reconstructed, or at least approximately reconstructed. According to embodiments, the defectometer is designed to determine, based on the deflections of beam paths, surface normals of the reflective surface of the object. Furthermore, the defectometer is designed to perform a topography determination of the object based on an integration of the surface normal. By determining the surface normals of the surface, it is easy to characterize local inclinations / gradients, wherein based on a plurality of the local inclinations an entire topography determination of the object can be carried out.

Embodiments according to the invention provide a reference pattern for topography determination of an object, the reference pattern having a first plurality of spirals and having a second plurality of spirals, wherein a winding direction the first plurality of spirals is opposite to a winding direction of the second plurality of spirals.

Embodiments according to the invention provide a method for topography tuning of an object. The method includes generating a reflection of a reference pattern on a surface of the object, the reference pattern having a first plurality of spirals and having a second plurality of spirals, wherein a winding direction of the first plurality of spirals is opposite to a winding direction of the second plurality of spirals , Furthermore, the method comprises detecting the reference pattern reflected by the object and providing topographical information based on the detected reflected reference pattern. The described method may be extended to include any or all features and functionalities described herein in connection with a device. Exemplary embodiments describe a method and a device for determining topographic deviations on rotationally symmetrical reflecting surfaces. Such test areas may e.g. spherical and aspherical lenses and mirrors, but also e.g. the cornea of the human eye previously measured with a concentric static pattern as shown in Figs.

Exemplary embodiments describe a method for recording deflectometric measurement data in polar coordinates with a static reference pattern, which however can also be in rotary motion. Embodiments according to the invention solve a problem of conventional concepts by the extension of a concentric reference stripe pattern on two opposing logarithmic spirals, which are perpendicular to each other everywhere and thus allow to measure both directions derivatives of the specular surface. According to embodiments of the invention, rotation of a concentric pattern allows the use of phase-measuring deflectometry, thus greatly reducing the measurement uncertainty. In addition, a static pattern is still used for the rotation, ie the geometry of the reference screen is freely selectable and can also be precalculated for the measurement of any spherical and aspheric surfaces so that the pattern reflected on the nominal shape can be evaluated as simply as possible. According to embodiments, a free configurability of the reference screen also allows to measure both convex and concave rotationally symmetric surfaces; In addition, the sensitivity of the measurement can be increased by the enlargement of the screen (and thus enlargement of the distances between the screen and the measurement object) within only practically prescribed limits.

Brief description of the figure

Embodiments according to the present invention will be explained below with reference to the accompanying figures. Show it:

Fig. 1 is a schematic representation of a deflectometer according to embodiments of the invention; Fig. 2 shows a reference pattern with conventional spirals, i. Archimedean spirals or arithmetic spirals, according to embodiments of the invention;

3 shows a reference pattern with logarithmic spirals, according to embodiments of the invention;

Fig. 4 shows a reference pattern with conventional spirals, i. Archimedean spirals or arithmetic spirals, according to embodiments of the invention, wherein a radius of the first plurality of spirals of a different pitch is subject to a radius of the second plurality of spirals;

5 illustrates a logarithmic spiral reference pattern according to embodiments of the invention, wherein a radius of the first plurality of spirals is subject to a different pitch than a radius of the second plurality of spirals;

Fig. 6 is a schematic illustration for phase measuring deflectometry;

FIG. 7 shows a schematic illustration for phase-measuring deflectometry; FIG. Phase information of the reference pattern of Fig. 2 generated by rotary detection;

Phase information of the reference pattern of Fig. 3 generated by rotary detection;

Phase information of the reference pattern of Fig. 4 generated by rotary detection;

Phase information of the reference pattern of Fig. 5 generated by rotary detection; a schematic illustration for generating the phase information according to Figures 8 to 11; a flowchart of a method according to embodiments of the invention; a conventional keratoscope; an evaluation of a shot of a conventional keratoscope; a photograph of a reflection of a stripe pattern of a conventional deflectometer on a spherical surface.

Detailed Description of the Embodiments

1 shows a schematic representation of a deflectometer 100 according to exemplary embodiments of the invention. The deflectometer 100 has a display 110 and an optional camera 15. Furthermore, the display 110 of the deflectometer 100 faces an object 120.

The display 110 is configured to render a reference pattern having a first plurality of spirals and a second plurality of spirals. Further, a winding direction of the first plurality of spirals is opposite to a winding direction of the second plurality of spirals. Furthermore, the deflectometer 100 is adapted to provide topographic information about the object based on a reflection of the reference pattern on the object 120.

The deflectometer 100 is configured to detect a reflection of the reference pattern on the object 120. For this purpose, the deflectometer 100 can be oriented in such a way that a surface of the object 120 to be examined faces the display 110. Based on the reflection, the deflectometer 100 can make a statement about the surface condition of the object 120. The deflectometer 100 is based on the idea that the plural numbers of spirals of the reference pattern produce an advantageous reflection for topography determination. In particular, spirals, for example in relation to circles, have the advantage that not only radial distortions of the pattern in the reflection are observable. Furthermore, the reflection of the reference pattern can serve to also observe tangential distortions. In general, the distortions in the reflection are created by unevenness of the surface of the object 120 and can thus serve to characterize it. Incidentally, the reference pattern can be used, for example, by a rotation of the reflection on the surface of the object 120, in order to enable a phase-measuring deflectometry. In this case, an at least tangentially periodic or even tangential and radial periodic intensity distribution of the reference pattern is advantageous. Due to the periodicity, an additive wave mixture of two sinusoidal intensity curves can be observed for a point on the pattern or its reflection during a rotation, as long as no distortion occurs. Based on the known intensity profile of the reference pattern, a reference phase can thus be derived. A deviation of the phase, which is observed in the reflection, can thus be used to determine a surface condition / topography by means of the reference phase.

FIG. 2 shows a reference pattern 200 with conventional spirals, ie Archimedean spirals or arithmetic spirals, according to embodiments of the invention, as can be reproduced on display 110, for example. The reference pattern 200 has a first plurality of spirals whose spiral arm centers 210a-k are drawn in, which have a first winding direction 2101. Furthermore, the reference pattern has a second plurality of spirals whose spiral arm centers 220a-i are drawn in, which have a second winding direction 220j. The spiral arm centers 210a-k of the first plurality of spirals are at a minimum of brightness of the first Plural of spirals, analogous to the Spiralarmzentren 220a-i, these may also be drawn in a brightness maximum of the first plurality of spirals, this represents only a phase offset. Further, the first winding direction 2101 is clockwise and the second winding direction 220j left-handed, in other words is the first winding direction 2101, the second winding direction 220j oriented opposite. Furthermore, the reference pattern 200 has a sinusoidal intensity profile on a circle concentric with a center of the first plurality of spirals or the second plurality of spirals. Since these are conventional spirals, the spacing of the spiral arm centers 210a-k and 220a-i in each winding remains constant. However, since the spirals in the reference pattern 200 have a small pitch, only a portion of a turn is visible and thus the constant spiral arm spacing is not observable. The first plurality of spirals and the second plurality of spirals, or their spiral arm centers 210a-k and 220a-i, have a constant slope of the radius which in the spirals of the first plurality of spirals is equal to the slope of the radius of the spirals of the second Is a plurality of spirals. The radius is subject to the formula

τ = αφ, (1) where a is the slope and φ the angle. Thus, for the first plurality of spirals and the second plurality of spirals a is equivalent. Furthermore, spirals of the respective pluralities of spirals have the same pitch. Since the spiral arms of the first plurality of spirals and the second plurality of spirals intersect at an angle that is close to 90 °, linearly independent base vectors can easily be calculated from their reflection, which can be used to simply estimate surface normals or independent slope parameters. For example, because the spiral arms do not intersect exactly perpendicularly for the described reference pattern 200, additional orthogonalization may be performed to obtain independent slopes, for example, via the Gram-Schmidt method. Furthermore, slope changes can be determined by differentiation of the slopes, wherein the slope changes describe curvatures of a surface of an object. By means of the estimated values, for example for the phase and direction of a first sine signal and a second sine signal, the surface texture or topography of an object, eg object 120, can consequently be determined with little effort. Incidentally, the spiral arm centers 210a-k and 220a-i are shown for illustrative purposes only, and are for use in deflectometry, generally, not in the reference. be visible 200. The same applies to the visibility of spiral alarm centers also for the reference patterns 300, 400 and 500 described below.

FIG. 3 shows a reference pattern 300 with logarithmic spirals, according to exemplary embodiments of the invention, as can be reproduced on the display 110, for example. Spiral center 310a-k, the first plurality of spirals, and spiral arm centers 320ai, the second plurality of spirals, are drawn into the reference pattern for illustrative purposes and will generally not be present if the reference pattern 300 is used for deflectometry, such as via the display 100. Further, the reference pattern 300 is similar to the reference pattern 200 where the radius of the first plurality of spirals and the second plurality of spirals is corresponding

r = be ^{k <} P (2), where b and k in reference pattern 300 are the same for the spirals of the first plurality of spirals and the second plurality of spirals. An advantage of reference pattern 300 over reference pattern 200 and other, for example, conventional, reference patterns is that the spiral arms are perpendicular to each other, or intersect at right angles, ie are orthogonal. For example, orthogonality can be used to directly determine slopes on the object that describe independent directions.

FIG. 4 shows a reference pattern 400 with conventional spirals, ie Archimedean spirals or arithmetic spirals, according to embodiments of the invention, as can be reproduced on display 110, for example. Analogous to reference pattern 200, the radii follow equation (1), where for the first plurality of spirals, indicated by spiral arm centers 410a-k, the slope a = a, and for the second plurality of spirals, characterized by spiral arm centers 420a-i, the slope a = a ₂ , where a ₂ >. In other words, the pitch of the first plurality of spirals is less than the pitch of the second plurality of spirals. Since, as with reference pattern 200, not more than one winding of each spiral is visible, the constant distance between a spiral arm over multiple windings is not apparent. However, the constancy of their gradients can already be read off indirectly from the constant radial spacings of the spirally wound spiral centers 410a-k. Since the spiral alarm density of the reference pattern 400 is radially higher than, for example, that of reference The reference pattern 400 is particularly suitable for detecting tilt errors on an object in the radial direction.

FIG. 5 shows a reference pattern 500 with logarithmic spirals, according to exemplary embodiments of the invention, as can be reproduced for example on the display 110. The reference pattern 500 has a first plurality of spirals with their spiral arm centers 510a-k drawn in, and a second plurality of spirals with their spiral arm centers 520a-i drawn. The radii of the first plurality of spirals and the second plurality of spirals are subject to equation (2), with the parameters b and k differing between the first plurality of spirals and the second plurality of spirals. The pitch, characterized by k, is greater for the second plurality of spirals than for the first plurality of spirals, and therefore the first plurality of spirals produces a higher swath density in the radial direction. Based on the higher density, equivalent to reference pattern 400, a higher precision of the topography determination in the radial direction can be achieved. Furthermore, since the reference pattern 500 corresponding to reference pattern 300 has orthogonal or intersecting points of the spiral arms of the first plurality of spirals spirals of the second plurality of spirals, two independent slope parameters can be estimated from the reflection of the reference pattern 500 with little effort.

In the following, recordings or acquisition series are considered, which are generated by rotation / rotation of either the reference pattern or the object. In general, the reference pattern is preferably rotated to accommodate rotated reflections, as objects, such as object 120, may be heavy or fragile objects or even patients. By means of the recordings, based on the periodic intensity profiles of the reference patterns 200, 300, 400 or 500, phase information for the topography determination can be obtained. In the following it will be briefly explained how phase-measuring deflectometry (PMD) is carried out by means of conventional stripe patterns.

FIG. 6 shows a schematic representation of a measurement setup 600 for the PMD. The measurement setup 600 has a display screen 610, a camera sensor 620 and a test object 630. On the display screen 610, a coordinate system is indicated with a first axis, which is marked with u, and a second axis, which is marked with v. Furthermore, a reference strip pattern is displayed on the display screen 610, which has a sinusoidal brightness curve in the v-direction. Furthermore, a reference strip pattern sequence 612 is displayed next to the display screen 610, which can be sequentially displayed on the display screen 610. The camera sensor 620 has a coordinate system with a first axis, marked x, and a second axis, labeled y. In this way, pixels of the camera sensor can be addressed by means of coordinates (x, y) and can be locally assigned. A light beam 622 is incident on the camera sensor 620 on the coordinate (x, y), which is sent from the display screen 610 and is directed to the camera sensor 620 via the test object 630. Since a surface normal 632 is tilted with respect to a mean surface normal 634 of the test object 630, the light beam images a point of the reference fringe pattern on the display screen 610 that is shifted from an expected point. The beam path 614 would image a predetermined point 616 of the display screen 610 on the camera sensor if the surface normal 632 corresponded to the mean surface normal 634. However, since the test object 630 has unevenness at the incident location of the beam path 622, a point 618 that does not correspond to the predetermined or expected point 616 is actually imaged on the camera sensor 620. Due to the fact that the reference fringe pattern is known, based on the shifted imaged spot 618, a first tilt direction of the surface of the test object 630 can now be determined at the point where the beam path 622 hits the surface. In further steps, further reference strip patterns of the reference strip pattern sequence 612 are displayed via the display screen 610 to determine a second direction of inclination of the surface. For improved accuracy, a previous calibration may take place and the pixels on the display screen 610 may be aligned with pixels of the camera sensor 620. For this purpose, a series of images can be displayed on the display screen 610, which includes both high and low frequency reference strip patterns.

In Fig. 7, said calibration process is illustrated. A camera maps a point P, on its image sensor, for example camera sensor 620, to a point P _L on the display screen, here an LCD screen. The image takes place via the beam path C, which is reflected over the surface S of the test object 630. For calibration, all or a majority of the pixels of the camera can be respectively assigned to a specific pixel of the display screen, so that the relative position in space of the camera sensor can be determined to the reference screen; This is also known as system orientation. In addition, for the correct interpretation of the tilt data, the spatial location of at least one point of the object surface is helpful, from which the above-mentioned integration starts, in order to obtain the surface topography from the measured phase or stripe distortions.

Fig. 8a shows phase information 800a of the first plurality of spirals based on a rotated shot of the reference pattern 200. The phase information 800a is based on a rotated shot of the reference pattern 200. The reference pattern 200 has 1 1 spiral arms in the first plurality of spirals, therefore Reference pattern should be recorded at least 23 times during a full revolution to meet the sampling theorem. The number of spiral arms in the first plurality of spirals and the number of spiral arms in the second plurality of spirals may be any natural numbers; if divisorless numbers are used, the assignment of the locations on the camera sensor to locations on the reference screen becomes easier. To generate the phase information 800a, 23 pictures of the reference pattern 200 were taken during a complete rotation. Based on the 23 images, a stack of images has been generated and each pixel along the time axis of the image stack has undergone discrete Fourier transformation to obtain one spectrum per pixel. The spectrum of the discrete Fourier transformation can be directly connected to the 1 1. Value are read out to obtain the frequency components (amplitude and phase) corresponding to the first plurality of spirals. This is because 1 1 spiral arms of the first plurality of spirals pass through the pixel during a complete rotation. Because of the regular arrangement of the spirals in the reference pattern 200, with an angle of 2π / 1 1 between tangentially adjacent spiral arms, there are exactly 1 1 stripes, the reading is exact. In other words, one can read the spectrum at the frequency corresponding to the number of spiral arms of the plurality of spirals for evaluation. Based on the value at the frequency, phase information can now be obtained since the discrete Fourier transformation provides a complex value. Furthermore, the phase of the complex value describes a shift, ie a rotation, of the original reference pattern. The phase information 800a encodes in dark to light a transition from 0 to 2π. Since the actual reference pattern generates waveforms based on the periodic intensity profile with more than 2π during one rotation, only the modulo-2 representation is reproduced here. In other words, as soon as the phase assumes a value of 2π, it is reset to 0 again. 8b shows a phase information 800b of the second plurality of spirals based on a rotated recording of the reference pattern 200. The generation of the phase information 800b is based essentially on the same steps as for the phase information 800a, and on exactly the same data set. To evaluate the phase, the ninth frequency index of the discrete Fourier transform is read out here and its phase determined. Here the reading at index 9 is exact. The index corresponds to the number of spirals in the second plurality of spirals. In light to dark, the phase curves are expressed from 0 to 2π, according to phase information 800a.

Fig. 8c shows a phase information 800c corresponding to the addition of the phase information 800a and 800b. The phase information 800c shows the intersections of the spiral arms by phase jumps, i. abrupt brightness changes in the phase information 800c, wherein the phase information 800c is the phase from 0 to 2π expressed by brightness variation from light to dark.

FIG. 9 a shows phase information 900 a based on rotated recordings of the reference pattern 300. In particular, the phase information 900a is based on the first plurality of spirals. The generation of the phase information 900a corresponds to the generation of the phase information 800a. For evaluation, the same frequency index can be used as for the phase information 800a because the number of spiral arms is identical. Dark to light gradients show the transition of the phase from 0 to Ζπ, where a modulo-2 representation is chosen due to the phase ambiguity. Since the number of spiral arms of the reference pattern 300 corresponds to the number of spiral arms of the reference pattern 200, the same sampling rate can be selected for detection.

FIG. 9 b shows phase information 900 b based on rotated recordings of the reference pattern 300. In particular, the phase information 900b is based on the second plurality of spirals. For evaluation, the same frequency index can be used as for the phase information 800b because the number of spiral arms is identical. Incidentally, for the phase information 900b, the descriptions given in connection with the above-mentioned phase information apply. Fig. 9c shows, according to Fig. 8c, a phase information 900c corresponding to the addition of the phase information 900a and the phase information 900b. The phase information tion 900c illustrates the mutually perpendicular spiral arms of the reference pattern 300 at the abrupt brightness changes.

FIGS. 10 a, 10 b, 10 c show phase information 1000 a, 1000 b and 1000 c, which are based on a rotated recording of the reference pattern 400. Incidentally, the descriptions given for the above-described phase information also apply to the phase information 1000a, 1000b and 1000c.

Figures 1 1 a, 1 1 b, 1 1 c show phase information 1 100a, 1100b and 1 100c, which are based on a rotated recording of the reference pattern 500. Incidentally, the descriptions given for the above-described phase information also apply to the phase information 1 100a, 1100b, and 1 00c.

Fig. 12 shows a pick-up stack 1200 which, depending on the reference pattern, can be used, for example, to generate the phase information 800a and 800b or 900a and 900b or 1000a and 1000b or 1100a and 1100b. The pickup stack 1200 is arranged in a coordinate system having 2 spatial axes, x, y, and a temporal axis, t. A pixel P ₀ (x _o, y _Q, 2N + 1) is located on the chronologically last recording 2N + 1 of the recording stack 1200th A possible intensity profile 1210 of the pixel P _Q is plotted over the time axis in graph 1210. The intensity curve in graph 1210 is characterized by a beat based on a first oscillation with 1 1 cycles per revolution and a second oscillation with 9 cycles per revolution. The periodicity is given by the numbers of spiral arms, the first plurality of spirals, and the second plurality of spiral arms, which in the considered case are 1 1 and 9. The intensity profile 1210 is periodic in φ and the phase of the pixel can be obtained directly by reading out the Fourier transform of the intensity curve 1210 at the frequency of the periodic signal. In this case, the periodicity of the intensity profile offers the advantage that the discrete Fourier transformation provides artifact-free results here. In graph 1220, the same intensity curve as in graph 1210 is shown oversampling, ie, 128 samples instead of 23, whereby a smoother waveform can be generated, serving only to better visualize the frequency mixture. Here, the beat, based on the addition of two periodic signals, very well recognizable. FIG. 13 shows a flowchart of a method 1300 according to embodiments of the invention. The method 1300 includes generating 1310 a reflection of a reference on a surface of the object, the reference pattern having a first plurality of spirals and a second plurality of spirals. Further, a winding direction of the first plurality of spirals is opposite to a winding direction of the second plurality of spirals. The method 1300 further comprises detecting 1320 the reference pattern reflected from the object. Furthermore, the method 1300 includes providing 1330 topographic information based on the detected reflected reference pattern.

The phase information 800a, 800b, 900a, 900b, 1000a, 1000b, 1100a, and 1100b show phases as they would be detected if no distortion occurred on a surface, and thus may serve as reference phase information.

In the following, further aspects of the inventive concept are treated, which can be used individually or in combination with the embodiments described herein.

Processes according to embodiments of the invention apply, according to conventional methods, also two perpendicular striped pattern; Although these are also crossed, but not straight, but as two opposing logarithmic spirals formed as shown in Fig. 3. The directions of the spirals are illustrated by the spiral arm centers 310a-k and 320a-i.

The pattern 300 is composed of a left-handed spiral with 9 arms and a right-handed spiral with 11 arms. Obviously, here the stripe pattern in the center may be too fine to evaluate; In practice, however, a camera will possibly be located here anyway. Nevertheless, consideration must be given to the outwardly geometrically growing fringe period (and thus decreasing inclination sensitivity) in the evaluation. On the other hand, the otherwise usually occurring compression of the strips in the edge region is already partly precompensated, so that it is possible to work with screens of weaker curvature or possibly even flat turntables.

Image acquisition may be accomplished by rotation of the reference structure, either over a full rotation of the reference disk (each spiral should be scanned a sufficient number of times, in this case more than 2x11 = 22 steps - in fact in the demonstration 23 images respectively rotated by 2rr / 23) and determination of the phases of the corresponding discrete frequency components by Fourier analysis (with the enormous advantage that the calculations are artifact-free, because the image data are obtained by a full rotation of the reference screen). and thus are really cyclical - which are also given tangential

Cyclicity of the slope data also provides a useful constraint for the integration of slope data, which is always to be done for shape determination by means of deflectometry). or

Via a partial rotation of the reference disk and evaluation of the phase data with frequency-selective phase shift formulas; Here it is sufficient to run 1-2 strips of each spiral on each image pixel, each strip having to be scanned with at least three images.

Rotation and data acquisition can be performed with cameras of appropriate frame rate in less than a second. If the image data stack is then examined for the signal phase at the predetermined frequencies, the separated phase functions 900a and 900b result, for example, as in FIGS. 9a and 9b (the phases of 0-2π being coded as light-dark).

Addition of both phase distributions, for example 900a and 900b, provides the visual demonstration in Figure 9c that the equiphase lines and thus the strips are perpendicular to each other everywhere.

In the previous example, reference patterns 300 and phase information 900a-c, the sensitivities are equally equally radial and tangential, but it is possible to set the slopes so that a component can be preferentially measured. The predetermined slopes of the spirals can be coupled so that the spiral arms are still intersecting at right angles everywhere. Fig. 5 shows a spiral pattern designed primarily for high sensitivity (proportional to the strip density) in the radial component (still having the left-hand spiral 9 arms and the right-handed 11 arms - these numbers are wide, practically only by choose the resolvable band density given limits). FIGS. 11a, 11b and 11c show the resulting phase distributions obtained from reference pattern 500.

Adjusting the spirals to exactly radial and tangential sensitivities is not readily possible because then the spirals would circle and rotation of the reference structure in one of the fringe patterns would no longer cause phase shifts, thus making phase calculation impossible. In any case, mixed slope components should be converted into radial and tangential fractions, but this is a simple task if the normal vectors are completely known on another basis.

Registering the phase data (i.e., uniquely associating the camera pixels with locations - not necessarily pixels - on the reference structure) is possible, on the one hand, through the use of prior knowledge of the surface, which can be rotationally symmetric, steadily and in very good approximation; on the other hand, by evaluating the phase values of both patterns on each camera pixel: if the numbers of spiral arms used are prime (for example, for 9 and 11), number-theoretic methods can be used for absolute registration, e.g. in [6]. Embodiments according to the invention simplify the use of deflectometry in applications such as e.g. ophthalmology, including the manufacture of contact and intraocular lenses, as well as the examination of aspheres. In all cases, annoying backside reflections may be caused by the use of e.g. Ultraviolet light can be avoided. The application with near or thermal infrared is conceivable.

According to embodiments, a static light pattern is used which, if necessary, can be applied to screens of any shape (but which are still rotationally symmetric) in a very high resolution. According to embodiments, sensitivities for tilt components in the radial and tangential directions can be freely balanced within wide limits.

According to embodiments, a sensitivity of the measurement can also be increased by enlarging the screen. According to embodiments, both convex and concave rotationally symmetric surfaces can be measured.

Exemplary embodiments describe a shape measurement on rotationally symmetrical spherical and aspherical surfaces of any size, for visible wavelengths, with possible extensions into the ultraviolet and near infrared.

In general, reflectometric measurements represent the slope components of a specular surface; therefore, data is usually recorded with two mutually perpendicular reference strip patterns. If it is not possible to use a monitor as a pattern display, you can work with a static screen that is moved along two axes for phase measurement and rotated by 90 ° in between. Alternatively, crossed patterns can be represented which allow phase measurements of both directional components in one direction only by means of displacements of the reference structure.

Some embodiments of the invention are based on the object, whether a similar method is possible with rotations of a mask to measure circular surfaces. We propose to represent crossed stripe patterns as contra-rotating spirals which are perpendicular to each other and thus allow linear independent phase measurements for the slope components. The evaluation of the data is more difficult than with Cartesian systems, but the sensitivities for radial or tangential pitch errors are selectable within wide limits. Further embodiments of the invention will now be described.

A first embodiment provides a deflectometer (100) for topography determination of an object (120), comprising: a display (110) adapted to provide a reference pattern (200, 300, 400);

500), wherein the reference pattern (200, 300, 400, 500) has a first plurality of spirals and a second plurality of spirals, wherein a winding direction (2101, 3101) of the first plurality of spirals is opposite to one

Winding direction (220j, 320j) of the second plurality of spirals, and wherein the deflectometer (100) is adapted to provide topographic information about the object (120) based on a reflection of the reference pattern on the object (120).

A 2. Ausführungsbeispie! 10 provides a deflectometer (100) according to the first embodiment, wherein the first plurality of spirals and the second plurality of spirals are concentrically arranged so that the first plurality of spirals and the second plurality of spirals have a common center.

A third embodiment provides a deflectometer (100) according to the first or second embodiment, wherein distances between spiral arms of the first plurality of spirals and / or the second plurality of spirals remain radially constant. A fourth embodiment provides a deflectometer (100) according to any one of the first to third embodiments wherein distances between spiral arms of the first plurality of coils and / or the second plurality of coils increase radially.

A fifth embodiment provides a deflectometer (100) according to the fourth embodiment, wherein the distances increase in geometric progression.

A sixth embodiment provides a deflectometer (100) according to any one of the first to fifth embodiments, wherein spiral arms of the first plurality of spirals and spiral arms of the second plurality of spirals intersect at an angle less than 180 ° and greater than zero ° is.

A seventh embodiment provides a deflectometer (100) according to the sixth embodiment, wherein the angle is 90 °. An eighth embodiment provides a deflectometer (100) according to any one of the first to seventh embodiments, wherein a first radius of the first plurality of spirals has a greater pitch than a second radius of the second plurality of spirals.

An embodiment 9 provides a deflectometer (100) according to any one of the first to eighth embodiments, wherein the display (110) is arranged relative to the object (120). a rejection of the reference pattern (200, 300, 400, 500) is produced on a reflective surface of the object (120).

A tenth embodiment provides a deflectometer (100) according to any of the first to ninth embodiments, wherein the deflectometer (100) comprises a camera disposed in a common center of the first plurality of spirals and the second plurality of spirals and wherein the camera is adapted to detect a reflection of the reference pattern (200, 300, 400, 500) on the object (120).

An 11th embodiment provides a deflectometer (100) according to one of the 1st to 10th embodiments, wherein the deflectometer (100) is designed to perform a topography determination of a rotationally symmetrical object or of a quasi-rotationally symmetrical object.

A twelfth embodiment provides a deflectometer (100) according to any one of the first to eleventh embodiments, wherein the deflectometer (100) is configured to rotate the reference pattern (200, 300, 400, 500) and the object (120) relative to one another , and wherein the deflectometer (100) is configured to obtain images of the rejections of the rotated reference pattern (200, 300, 400, 500) based on the rotation.

A thirteenth embodiment provides a deflectometer (00) according to any one of the first to twelfth embodiments, wherein the deflectometer (100) is configured to rotate the reference pattern (200, 300, 400, 500) on the display (110), and wherein the deflectometer (100) is adapted to obtain images of the rejections of the rotated reference pattern (200, 300, 400, 500) based on the rotated reproduction.

An embodiment of the present invention provides a deflectometer (100) according to the 12th or 13th embodiment, wherein the deflectometer (100) is adapted to perform the topography determination on the basis of phase information. wherein the deflectometer (100) is configured to obtain the phase information based on the images of the reflections of the rotated reference pattern (200, 300, 400, 500). A 15th embodiment provides a deflectometer (100) according to the 14th embodiment, wherein the deflectometer (100) is adapted to obtain the phase information based on a discrete Fourier transform of the recordings of the reflections of the rotated reference pattern. A 16th embodiment provides a deflectometer (100) according to the 14th embodiment, wherein the deflectometer (100) is configured to obtain the phase information based on phase shift formulas from the images of the reflections of the rotated reference pattern (200, 300, 400, 500). A 17th embodiment provides a deflectometer (100) according to any one of the first to sixteenth embodiments, wherein the deflectometer (100) is configured based on shooting a rotated reproduction of the reference pattern (200, 300, 400, 500) from the first plurality to obtain first phase information from spirals, and to obtain second phase information based on recordings of a rotated reproduction of the reference pattern (200, 300, 400, 500) from the second plurality of spirals, and wherein the deflectometer (100) is designed, a topography designation based on the first phase information and the second phase information.

An 18th embodiment provides a deflectometer (100) according to any one of the 14th to 17th embodiments, wherein the deflectometer (100) is configured to determine deflections of optical paths based on the phase information, and wherein the deflectometer (100) is designed based on the deflections of optical paths to determine a plurality of pitch parameters of a reflective surface of the object (120). A 19th embodiment provides a deflectometer (100) according to the 18th embodiment, wherein the deflectometer (100) is designed based on integration of Plurality of slope parameters to perform the topography determination of the object (120).

A 20th embodiment provides a deflectometer (100) according to the 19th embodiment, wherein the deflectometer (100) is configured to determine, based on the deflections of optical paths, finned normals of the reflective surface of the object (120), and wherein the deflectometer (100) is adapted to perform a topography determination of the object (120) based on an integration of the area normal.

A 21st embodiment provides a reference pattern (200, 300, 400, 500) for topography determination of an object (120), the reference pattern having a first plurality of spirals and having a second plurality of spirals, wherein a winding direction (2101, 3101 ) of the first plurality of spirals is opposite to a winding direction (220j, 320j) of the second plurality of spirals.

A 22th embodiment provides a method (1300) for topography determination of an object (120), comprising the following steps:

Generating (1310) a reflection of a reference pattern (200, 300, 400, 500) on a surface of the object (120), the reference pattern (200, 300, 400, 500) comprising a first plurality of spirals and a second plurality of spirals, wherein a winding direction (2101, 3101) of the first plurality of spirals is opposite to a winding direction (220j, 320j) of the second plurality of spirals,

Detecting (1320) the reference pattern (200, 300, 400, 500) reflected by the object (120), and

Providing (1330) topographic information based on the detected reference reflected pattern (200, 300, 400, 500). A 23rd embodiment provides a computer program with a program code for

Execution of the method according to the 22nd embodiment, when the program runs on a computer.

Although some aspects have been described in the context of a device, it will be understood that these aspects also constitute a description of the corresponding method, so that a block or a component of a device is also to be understood as a corresponding method step or as a feature of a method step , Similarly, aspects described in connection with or as a method step also represent a description of a corresponding block or detail or feature of a corresponding device. Some or all of the method steps may be performed by a hardware device (or using a hardware device). Apparatus), such as a microprocessor, a programmable computer or an electronic circuit. In some embodiments, some or more of the most important method steps may be performed by such an apparatus.

An encoded signal according to the invention, such as an audio signal or a video signal or a transport stream signal, may be stored on a digital storage medium or may be transmitted on a transmission medium such as a wireless transmission medium or a wired transmission medium, eg the Internet. Depending on particular implementation requirements, embodiments of the invention may be implemented in hardware or in software. The implementation may be performed using a digital storage medium, such as a floppy disk, a DVD, a Blu-ray Disc, a CD, a ROM, a PROM, an EPROM, an EEPROM or FLASH memory, a hard disk, or other magnetics Viewing or optical storage are carried on the electronically readable control signals are stored, which can cooperate with a programmable computer system or cooperate such that the respective method is performed. Therefore, the digital storage medium can be computer readable. Some embodiments according to the invention thus comprise a data carrier which has electronically readable control signals which are capable of being used with a pro- programmable computer system such that one of the methods described herein is performed.

In general, embodiments of the present invention may be implemented as a computer program product having a program code, wherein the program code is operable to perform one of the methods when the computer program product runs on a computer.

The program code can also be stored, for example, on a machine-readable carrier.

Other embodiments include the computer program for performing any of the methods described herein, wherein the computer program is stored on a machine-readable medium.

In other words, an embodiment of the method according to the invention is thus a computer program which has a program code for performing one of the methods described herein when the computer program runs on a computer.

A further embodiment of the inventive method is thus a data carrier (or a digital storage medium or a computer-readable medium) on which the computer program is recorded for carrying out one of the methods described herein. The data carrier, the digital storage medium or the computer-readable medium are typically representational and / or non-transitory.

A further exemplary embodiment of the method according to the invention is thus a data stream or a sequence of signals which represents or represents the computer program for carrying out one of the methods described herein. The data stream or the sequence of signals may be configured, for example, to be transferred via a data communication connection, for example via the Internet. Another embodiment includes a processing device, such as a computer or a programmable logic device, that is configured or adapted to perform one of the methods described herein. Another embodiment includes a computer on which the computer program is installed to perform one of the methods described herein.

Another embodiment according to the invention comprises a device or system adapted to transmit a computer program for performing at least one of the methods described herein to a receiver. The transmission can be done for example electronically or optically. The receiver may be, for example, a computer, a mobile device, a storage device or a similar device. For example, the device or system may include a file server for transmitting the computer program to the recipient.

In some embodiments, a programmable logic device (eg, a field programmable gate array, an FPGA) may be used to perform some or all of the functionality of the methods described herein. In some embodiments, a field programmable gate array may cooperate with a microprocessor to perform one of the methods described herein. In general, in some embodiments, the methods are performed by any hardware device. This may be a universal hardware such as a computer processor (CPU) or hardware specific to the process, such as an ASiC.

For example, the devices described herein may be implemented using a hardware device, or using a computer, or using a combination of a home appliance and a computer. The devices described herein, or any components of the devices described herein, may be implemented at least in part in hardware and / or software (computer program).

The methods described herein may be implemented, for example, using a hardware device, or using a computer, or using a combination of a hardware device and a computer. The methods described herein, or any components of the methods described herein, may be performed at least in part by hardware and / or by software.

The embodiments described above are merely illustrative of the principles of the present invention. It will be understood that modifications and variations of the arrangements and details described herein will be apparent to others of ordinary skill in the art. Therefore, it is intended that the invention be limited only by the scope of the appended claims and not by the specific details presented in the description and explanation of the embodiments herein.

References:

[1] Liu, Y .; Olesch, E .; Yang, Z. & Häusler, G. Fast and accurate reflectometry with crossed fringes, Advanced Optical Technologies, 2014, 3, 441-445

[2] Hibino, K .; Hanayama, R .; Burke, J. & Oreb, B.F. Tunable phase-extraction formule for simultaneous shape measurement of multiple surfaces with wavelength-shifting interferometry, Optics Express, 2004, 12, 5579-5594

[3] Krey, S .; van Amstei, W. D .; Szwedowicz, K .; Campos, J .; Moreno, A. & Lous, E.J.

A fast optical scanning deflectometer for measuring the topography of large silicon wafers, Proc. SPIE, Current Developments in Lens Design and Optical Engineering V, 2004, 5523, 110-120

[4] Liang, H .; Olesch, E .; Yang, Z. & Häusler, G. Single-shot phase-measuring deflectometry for Cornea measurement, Advanced Optical Technologies, 2016, 5, 1-6

[5] Zhao, W .; Su, X .; Liu, Y. & Zhang, Q. Testing an aspheric mirror based on phase measuring deflectometry, Optical Engineering, 2009, 48, 103603

[6] Falaggis, K .; Towers, D.P. & Towers, C.E. Algebraic Solution for phase unwrapping Problems in multiwavelength interferometry, Appl. Opt, 2014, 53, 3737-3747

Claims

claims

Defectometer (100) for topography determination of an object (120), comprising: a display (110) adapted to render a reference pattern (200, 300, 400, 500), the reference pattern (200, 300, 400, 500) has a first plurality of spirals and a second plurality of spirals, wherein a winding direction (2101, 3101) of the first plurality of spirals is opposite to a winding direction (220j, 320j) of the second plurality of spirals, the defectometer (100 ) is adapted to provide topographic information about the object (120) based on a reflection of the reference pattern on the object (120), the defectometer (100) being arranged to rotate the reference pattern (200, 300, 400, 500) on the object Display (110), wherein the Defiektometer (100) is adapted to receive based on the rotated playback recordings of the reflections of the rotated reference pattern (200, 300, 400, 500), wherein the D efiectometer (100) is adapted to perform the topography determination based on phase information, wherein the defiectometer (100) is adapted to obtain the phase information based on the images of the reflections of the rotated reference pattern (200, 300, 400, 500), and wherein the defiectometer (100) is adapted to obtain the phase information based on a discrete Fourier transform of the recordings of the reflections of the rotated reference pattern. A deflectometer (100) for topography determination of an object (120), comprising: a display (110) adapted to render a reference pattern (200, 300, 400, 500), the reference pattern (200, 300, 400, 500) 500) has a first plurality of spirals and a second plurality of spirals, wherein a winding direction (2101, 3101) of the first plurality of spirals is opposite to a winding direction (220j, 320j) of the second plurality of spirals, wherein the deflectometer (100) is adapted to provide topographic information about the object (120) based on a reflection of the reference pattern on the object (120), the deflectometer (100) being configured based on images of a rotated representation of the reference pattern (200, 300 , 400, 500) of the first plurality of spirals to obtain first phase information, and based on recordings of a rotated representation of the reference pattern (200, 300, 400, 500) the second plurality of spirals to obtain second phase information, and wherein the deflectometer (100) is configured to obtain a topography determination based on the first phase information and the second phase information.

A deflectometer (100) for topography determination of an object (120), comprising: a display (110) adapted to render a reference pattern (200, 300, 400, 500), wherein the reference pattern (200, 300, 400, 500) has a first plurality of spirals and has a second plurality of spirals, wherein a winding direction (2101, 3101) of the first plurality of spirals opposite to a winding direction (220j, 320j) the second plurality of spirals, wherein the deflectometer (100) is configured to provide topographic information about the object (120) based on a reflection of the reference pattern on the object (120), and distances between spiral arms of the first plurality of spirals and or the second plurality of spirals increase radially in geometric progression such that the spirals are logarithmic spirals.

4. A deflectometer (100) according to any one of claims 1 to 3, wherein the first plurality of spirals and the second plurality of spirals are concentrically arranged so that the first plurality of spirals and the second plurality of spirals have a common center.

5. A deflectometer (100) according to claim 1 or 2, wherein distances between spiral arms of the first plurality of spirals and / or the second plurality of spirals remain radially constant.

6. A deflectometer (100) according to claim 1 or 2, wherein distances between spiral arms of the first plurality of spirals and / or the second plurality of spirals increase radially.

7. Deflectometer (100) according to claim 6, wherein the distances increase in geometric progression.

The deflectometer (100) of any one of claims 1 to 7, wherein spiral arms of the first plurality of spirals and spiral arms of the second plurality of spirals intersect at an angle that is less than 180 ° and greater than 0 °.

9. Deflectometer (100) according to claim 8, wherein the angle is 90 °. 10. Deflectometer (100) according to one of claims 1 to 9, wherein a first radius of the first plurality of spirals has a greater pitch than a second radius of the second plurality of spirals.

A deflectometer (100) according to any one of claims 1 to 10, wherein the display (110) is disposed relative to the object (120) such that reflection of the reference pattern (200, 300, 400, 500) on a reflective surface of the object (120 ) is produced.

The deflectometer (100) of any one of claims 1 to 11, wherein the deflectometer (100) comprises a camera disposed in a common center of the first plurality of spirals and the second plurality of spirals and wherein the camera is configured to provide a reflection of the reference pattern (200, 300, 400, 500) on the object (120).

13. Deflectometer (100) according to one of claims 1 to 12, wherein the deflectometer (100) is designed to perform a Topografiebestimmung a rotationally symmetric object or a quasi-rotationally symmetric object.

14. A deflectometer (100) according to any one of claims 1 to 13, wherein the deflectometer (100) is adapted to rotate the reference pattern (200, 300, 400, 500) and the object (120) relative to each other, and wherein the deflectometer ( 100) is adapted to obtain based on the rotation recordings of the reflections of the rotated reference pattern (200, 300, 400, 500).

The deflectometer (100) of any one of claims 1 to 14, wherein the deflectometer (100) is configured to determine deflections of optical paths based on the phase information, and wherein the deflectometer (100) is configured based on the deflections of optical paths Determine a plurality of slope parameters of a reflective surface of the object (120). The defibrometer (100) of claim 15, wherein the defibrometer (100) is configured to perform the tomography determination of the object (120) based on integration of the plurality of slope parameters.

The defectometer (100) of claim 16, wherein the defectometer (100) is configured to determine surface normal of the reflective surface of the object (120) based on the deflections of optical paths, and wherein the defectometer (100) is configured based on integration the surface normal perform a topography determination of the object (120).

Reference pattern (200, 300, 400, 500) for topography determination of an object (120), the reference pattern having a first plurality of spirals and having a second plurality of spirals, wherein a winding direction (2101, 3101) is opposite to the first plurality of spirals a winding direction (220j, 320j) of the second plurality of spirals, and wherein spacings between spiral arms of the first plurality of spirals and / or the second plurality of spirals increase radially in geometric progression such that the spirals are logarithmic spirals.

Method (1300) for topography determination of an object (120), comprising the following steps:

Generating (1310) a mirror of a reference pattern (200, 300, 400, 500) on a surface of the object (120), wherein the reference pattern (200, 300, 400, 500) comprises a first plurality of spirals and a second plurality of spirals wherein a winding direction (2101, 3101) of the first plurality of spirals is opposite to a winding direction (220j, 320j) of the second plurality of spirals, Detecting (1320) the reference pattern (200, 300, 400, 500) reflected by the object (120), and

Providing (1330) topographic information based on the detected reference reflected pattern (200, 300, 400, 500), the reference pattern (200, 300, 400, 500) being displayed in rotation on the display (110), based on the rotated Playback images of the reflections of the rotated reference pattern (200, 300, 400, 500) are obtained, wherein the Topografiebestimmung is performed based on phase information, the phase information based on the images of the reflections of the rotated reference pattern (200, 300, 400, 500) receive and the phase information is obtained based on a discrete Fourier transform of the recordings of the reflections of the rotated reference pattern.

Generating (1310) a mirror of a reference pattern (200, 300, 400, 500) on a surface of the object (120), wherein the reference pattern (200, 300, 400, 500) comprises a first plurality of spirals and a second plurality of spirals wherein a winding direction (2101, 3101) of the first plurality of spirals is opposite to a winding direction (220j, 320j) of the second plurality of spirals,

Detecting (1320) the reference pattern (200, 300, 400, 500) reflected by the object (120), and Providing (1330) topographic information based on the detected reference reflected pattern (200, 300, 400, 500), wherein based on recordings of a rotated representation of the reference pattern (200, 300, 400, 500) from the first plurality of spirals, first phase information wherein a second phase information is obtained based on recordings of a rotated reproduction of the reference pattern (200, 300, 400, 500) from the second plurality of spirals, and wherein a topography determination is obtained based on the first phase information and the second phase information.

21. Method (1300) for topography determination of an object (120), comprising the following steps:

Generating (1310) a reflection of a reference pattern (200, 300, 400, 500) on a surface of the object (120), wherein the reference pattern (200, 300, 400, 500) comprises a first plurality of spirals and a second plurality of spirals wherein a winding direction (2101, 3101) of the first plurality of spirals is opposite to a winding direction (220j, 320j) of the second plurality of spirals, and wherein spacings between spiral arms of the first plurality of spirals and / or the second plurality of spirals are radial increase in geometric progression, so that the spirals are logarithmic spirals

Providing (1330) topographic information based on the detected reference reflected pattern (200, 300, 400, 500).

22. A computer program with a program code for carrying out the method according to claim 17 or 18, when the program runs on a computer.