DE10317828B3 - Interferometric investigation of measurement object involves forming measurement and reference beams in first interferometer unit, scanning object and passing reflected beams to second unit with reference beams - Google Patents

Abstract

The method involves illuminating a modulator (9) with incoherent or short coherence light with differently coded components, forming separate beams from the components and coupling into a first interferometer unit (18) to form measurement (21,22) and reference beams. The measurement beams are separately scanned over the object (1). Reflected beams are fed with reference beams to a second interferometer unit (27). Interfering components are evaluated. The method involves illuminating a spatial light modulator with incoherent or short coherence light with at least two differently coded components, forming separate light beams from the different components and coupling them into a first interferometer unit that forms measurement and reference beams. The measurement beams are separately scanned over the object surface. The reflected beams are fed with their reference beams to a second interferometer unit and interfering components are evaluated. An independent claim is also included for the following: (a) an arrangement for interferometric investigation of measurement object.

Description

The invention relates to a method and a device for the interferometric examination of a Measurement object, the device being at least one incoherent or short-coherent source light emitting light source, a source light in reference light and measuring light dividing first interferometer unit and coupling means of the measurement light reflected by the measurement object and the reference light into a second interferometer unit and a detector Evaluation device includes.

An interferometric method and an interferometric measuring device of the aforementioned type have been developed for the purpose of absolute distance measurement DE 195 20 305 A1 known. A single measurement light bundle is then reflected on a measurement object, which is located at a specific distance to be determined from a reference object, namely a beam splitter of the first interferometer unit. This distance creates an optical path difference between the reference light beam and the measurement light beam, which corresponds to twice the distance to be determined. The reference light bundle and measurement light bundle are fed to the second interferometer unit. Different optical paths in the second interferometer unit compensate for the optical path difference between the measurement light bundle and the reference light bundle, so that information about the distance to be measured can be made via interference between the measurement light bundle and the reference light bundle in the second interferometer unit.

From the US 2003/0025913 A1 an interferometric measuring method and an interferometric measuring device for short-coherent light are known, according to which a surface is scanned with a measuring light beam. Frequency coding of the measurement light is used, which serves to differentiate between different optical delays, so that different depths on the measurement object can be measured simultaneously.

It is now the task of the present Invention, a method and an apparatus of the aforementioned Kind available to provide, which allow a significantly increased measuring speed.

• a) ein eine Vielzahl von einzeln schaltbaren und/oder steuerbaren Modulatorelementen aufweisender räumlicher Lichtmodulator mit inkohärentem oder kurzkohärentem Quelllicht flächig beleuchtet wird, wobei mindestens zwei Anteile des Quelllichts auf unterschiedliche Weise codiert werden und jeder unterschiedlich codierte Anteil einen anderen Bereich des räumlichen Lichtmodulators flächig beleuchtet,
• b) mittels der Modulatorelemente aus jedem unterschiedlich codierten Anteil des Quelllichts ein separates Quelllichtbündel gebildet und in eine erste Interferometereinheit eingekoppelt wird,
• c) in der ersten Interferometereinheit jedes Quelllichtbündel jeweils in ein Messlichtbündel und ein zugehöriges Referenzlichtbündel aufgeteilt wird,
• d) die Messlichtbündel flächig voneinander getrennt über die zu untersuchende Messobjektoberfläche gerastert werden,
• e) die von der Messobjektoberfläche reflektierten Messlichtbündel und die zugehörigen Referenzlichtbündel einer zweiten Interferometereinheit zugeführt werden,
• f) in der zweiten Interterometereinheit Anteile jedes Messlichtbündels jeweils mit Anteilen des zugehörigen Referenzlichtbündels nach Durchlaufen unterschiedlicher optischer Wegstrecken überlagert und auftretende Interferenzen in Zuordnung zur jeweiligen optischen Wegstrecke festgestellt werden, und
• g) die von den miteinander interferierenden Anteilen des Messlichts und des zugehörigen Referenzlichts in der zweiten Interferometereinheit zurückgelegten optischen Wegstrecken nach den Codierungen getrennt ausgewertet werden.

This object is achieved with a method of the type mentioned at the beginning, in which

• a) a spatial light modulator having a plurality of individually switchable and / or controllable modulator elements is illuminated areally with incoherent or short-coherent source light, at least two parts of the source light being coded in different ways and each differently coded part illuminating a different area of the spatial light modulator areally,
• b) by means of the modulator elements, a separate source light bundle is formed from each differently coded portion of the source light and is coupled into a first interferometer unit,
• c) in the first interferometer unit, each source light bundle is divided into a measurement light bundle and an associated reference light bundle,
• d) the measurement light bundles are scanned across the surface of the measurement object to be examined,
• e) the measurement light bundles reflected by the surface of the measurement object and the associated reference light bundles are fed to a second interferometer unit,
• f) in the second interterometer unit, portions of each measurement light bundle are overlaid with portions of the associated reference light bundle after passing through different optical paths and interferences occurring are determined in association with the respective optical path, and
• g) the optical distances covered by the interfering portions of the measurement light and the associated reference light in the second interferometer unit are evaluated separately according to the codings.

Because in this way the surface of the measuring object at least two measuring light bundles is rasterized at the same time, compared to the above State of the art the measurement speed accordingly by at least increased by a factor of two become. In addition, measurements can be carried out with great flexibility. That's the way it is e.g. possible, the measuring light bundles independently from each other about just rasterize the areas of the object surface that are in particular Interesting way. There is a scanning of the entire surface therefore not necessary.

The method according to the invention can also be carried out in such a way that a digital mirror unit (DMD) is used as the spatial light modulator. Such micromirrors are, for example, from the DE 198 11 202 C2 known where they are used to scan a surface to be measured with a plurality of light points in a confocal scanning microscope. The individual micromirror elements of the mirror unit can be controlled independently of one another, so that groups of micromirror elements can each be responsible for one source light beam. Alternatively, a source light beam can also be generated by a single micromirror element.

The method according to the invention can also be carried out such that as a spatial light mo a liquid crystal display (LCD) is used. The liquid crystal display can be switched opaque to the radiation used for certain areas, so that separate source light beams can be generated.

The method according to the invention can be carried out that color coding is used by the source light in at least two portions with different wavelengths or different wavelength ranges is divided. Source light beam with different wavelengths can completely independently from each other via the Target surface guided and evaluated separately.

Alternatively, it is also possible that inventive method to do so that an intensity coding is used by the source light in at least two parts with different intensity values is divided.

The method according to the invention can also be carried out that the surface topography of the measurement object or a three-dimensional depth profile of the measurement object is determined.

• a) jedes Messlichtbündel und jedes Referenzlichtbündel in der zweiten Interferometereinheit jeweils in ein erstes und ein zweites Teilbündel aufgeteilt wird,
• b) jedes erste Messlichtteilbündel und jedes erste Referenzlichtteilbündel einen ersten Strahlengang durchläuft und dabei an einem mindestens ein Messstufenfeld aufweisenden Stufenkörper reflektiert wird, wobei die optische Wegstrecke im ersten Strahlengang vom Ort der Reflexion auf dem Stufenkörper abhängt,
• c) jedes zweite Messlichtteilbündel und jedes zweite Referenzlichtteilbündel einen zweiten Strahlengang der zweiten Interferometereinheit durchläuft,
• d) sämtliche Teilbündel einem Detektor zugeführt werden, der sich am Ende einer beiden Strahlengängen gemeinsamen Interferenzstrecke befindet,
• e) die Stufen des mindestens einen Messstufenfeldes optisch auf ein Bildsensorfeld des Detektors abgebildet werden und
• g) die Position der Abbildungen von zwischen jedem Messlichtteilbündel und dem zugehörigen Referenzlichtteilbündel auftretenden Messinterferenzen in der Abbildung des Messstufenfeldes auf dem Detektor zur Messung herangezogen wird.

It can be advantageous to carry out the method according to the invention in such a way that

• a) each measurement light bundle and each reference light bundle in the second interferometer unit is divided into a first and a second sub-bundle,
• b) each first measuring light sub-bundle and each first reference light sub-bundle passes through a first beam path and is thereby reflected on a step body having at least one measuring step field, the optical path in the first beam path depending on the location of the reflection on the step body,
• c) every second measurement light sub-bundle and every second reference light sub-bundle passes through a second beam path of the second interferometer unit,
• d) all sub-bundles are fed to a detector which is located at the end of an interference path common to both beam paths,
• e) the steps of the at least one measuring step field are optically mapped onto an image sensor field of the detector and
• g) the position of the images of measurement interferences occurring between each measurement light partial bundle and the associated reference light partial bundle in the image of the measurement stage field on the detector is used for the measurement.

Due to the short coherence length of the only the proportion of the reference light sub-bundle interferes with the light used the associated Measuring light partial bundle, that reflects at the location on the step body that creates the appropriate path has been. This is the case when in the first interferometer unit generated distance difference between the reference light beam and the measuring light beam was compensated in the second interterometer unit. The measurement interference between the superimposed ones Partial light bundles is in together with the reflective surface of the step body a plane perpendicular to the optical axis optically onto the image sensor field of the detector. In this figure, the measurement interference generating reflection point on the step body determined and from there and from the known optical path lengths directly to one value to be determined, e.g. B. a distance to be closed.

• a) der Stufenkörper derart angeordnet wird, dass eine durch Reflexion an der Reflexionsfläche einer Kalibrierstufe erzeugte optische Kalibrierwegstrecke im ersten Strahlengang mit der optischen Wegstrecke im zweiten Strahlengang exakt übereinstimmt,
• b) die Kalibrierstufe ebenfalls optisch auf das Bildsensorfeld des Detektors abgebildet wird und
• c) die durch die jeweilige Überlagerung der Messlichtteilbündel mit dem zugehörigen Referenzlichtteilbündel beim Durchlaufen der Kalibrierwegstrecke und des zweiten Strahlenganges in der Interferenzstrecke erzeugten Kalibrierinterferenzen zur Überprüfung der Position des Stufenkörpers festgestellt werden

The method according to the invention can also be carried out in such a way that

• a) the step body is arranged in such a way that an optical calibration path in the first beam path generated by reflection on the reflection surface of a calibration step corresponds exactly to the optical path in the second beam path,
• b) the calibration stage is also imaged optically on the image sensor field of the detector and
• c) the calibration interferences generated by the respective superimposition of the measuring light partial bundles with the associated reference light partial bundles when passing through the calibration path and the second beam path in the interference path are ascertained to check the position of the step body

If the calibration distance is the same with that of the second beam path in the second interferometer unit also with short-coherent Light always creates an interference, the calibration interference, namely between the two sub-beams of each reference light beam or measurement light beam, because each one - share the sub-bundle passing through the first beam path at the calibration stage is reflected. If such a calibration interference is detected, is certain that the step body is correctly positioned within the second measurement interferometer. From the known geometry of the step body and from the position The measurement interference in the area of the measurement levels can then be directly the size to be measured, e.g. B. a distance to be determined.

If the reflection surface of the calibration stage is exactly perpendicular to the optical axis of the first beam path, the calibration interference only occurs when the stage body is in the appropriate position and would have to be readjusted accordingly if there is no calibration interference. Because of this, it can be advantageous to carry out the method according to the invention in such a way that the step body is arranged in such a way that the surface normals of the reflection surfaces of the calibration step and / or the steps of the measurement step field are inclined to the optical axis of the first beam path, and the position of the calibration interference in the Illustration the reflection surface of the calibration stage is determined on the detector and used to calibrate the measurement result.

With a suitable expansion of the Calibration level perpendicular to the tilt axis is for the position of the step body in the second interferometer unit is given adequate scope. With the detector it can be determined from which location on the Calibration level the reflection generating the calibration interference emanates. In the event of position shifts due to mechanical influences and / or Thermal expansion effects this position can shift on the calibration level. This shift is determined and for the calculation of the size to be measured is taken into account. A position adjustment mechanical displacement of the step body is therefore superfluous. There both the calibration interference and the measurement interference at the same time can be evaluated is an ongoing calibration during measurement possible. The inclination of the measuring stage fields to the optical axis can be selected that a continuous measuring range is covered. Alternatively or also additionally the calibration level and the measurement levels in to be graded again, taking the direction of this substation is perpendicular to that of the main grading.

The method according to the invention can also be carried out that the calibration level and / or the levels of the measurement level field individually and in each case by means of separate optical means on each one or two image sensor lines adjacent to one another are imaged become. For this purpose, it can be advantageous as separate optical means Use rod lenses. Finally it can also be advantageous to read only the image sensor lines, to the the steps of the step body be mapped. The use of rod lenses has the advantage that the mapping of the individual stages on the image sensor lines with increased intensity he follows. In addition, only the image sensor lines need to be read out which levels of the measurement level field are shown, which means the measuring speed can be increased significantly. It could also make sense, the order of reading the individual image sensor lines dependent from the expected measurement result. Is z. B. with the inventive method a continuously changing distance in a certain direction by a Large number of measurements checked, based on the most recent measurement results a tendency can be determined from the one to be expected for the next future measurement Measurement result can be derived. The expected measurement result could then serve to define the image sensor line that is read out first becomes. As long as no measurement interference is found, the neighboring image sensor lines read out. However, it is constantly read out the image sensor line to which the calibration level and the calibration interference are shown.

The task mentioned above will continue solved by a device of the type mentioned a coding unit with at least two surfaces separated from one another Coding areas for coding the source light, in the beam direction the source light seen behind the coding unit and before the first Interterometer unit from a differently coded source light spatially illuminated in different areas Light modulator with a variety of individually switchable and / or controllable Modulator elements that are used to control at least two surfaces against each other Delimited, differently coded source light bundles can be generated are, and an evaluation device for separate after coding Evaluation.

Further advantageous configurations of the inventions result from subclaims 15 to 24.

An advantageous embodiment of the method according to the invention and an advantageous embodiment of the device according to the invention are explained below with reference to figures.

They show schematically

1 : a device for measuring the surface topography of a measurement object,

2 : a coding plate for color coding,

3 : a coding plate for an intensity coding,

4 : a graphic to show the dependence of the transmissivity of the coding plate according to 3 .

5 : a step body,

6 : a housing and a housing holder for a detector optics,

7 : a side section through the detector optics with housing and housing holder and

8th : a cut oblique view of the housing with rod lenses.

1 shows a device with which the surface topography of a measurement object 1 can be determined. Short-coherent light from a light source 2 is by means of a coupling optics 3 into an optical fiber 4 coupled and via an expansion optics 5 as a parallel source light beam 6 on a beam cube 8th directed. From there the source beam of light 6 on a DMD unit 9 (Digital Mirror Decvice). The DMD unit 9 consists of a large number of individually movable and controllable micromirror elements, which are not shown in detail here. Before hitting the DMD unit 9 passes through the source light beam 6 a coding plate 10 , It can be a color coding plate 11 act as they do in 2 is shown schematically. The color coding plate 11 is exemplary here in three zones 12 . 13 and 14 divided, which are selectively transmissive for different wavelengths λ1, λ2, λ3. According to the coding by the coding plate 10 meet the DMD unit 9 now three source light beams with different wavelengths. Using the micromirror elements of the DMD unit 9 each source light beam becomes a source light beam 15 . 16 generated, of which in 1 only two are shown. The source light bundle 15 and 16 pass through a second beam splitter cube 17 and a Mirau interferometer as the first interferometer unit 18 and then hit the surface of the object to be examined 1 , The Mirau interferometer 18 includes two beam splitter plates 19 and 20 , The proportion of each source light beam 15 . 16 on the rear beam splitter plate 20 is reflected and the measurement object 1 not reached, forms a reference light beam. The proportion of the source light bundle 15 . 16 that reaches the measurement object is a measurement beam 21 . 22 ,

Both the reference light bundles not shown separately here and those of the measurement object 1 reflected measurement light bundle 21 . 22 are over the second beam split cube 17 via a second coupling optics 23 into an optical fiber cable 24 fed. Via a second expansion lens 25 become the reference light beam and measurement light beam 21 . 22 as parallel bundles on a third beam splitter cube 26 of a Michelson interferometer 27 given. At the third beam splitter cube 26 become parts of the measuring light bundle 21 . 22 and reference light beam in the direction of a step mirror 28 directed. The step mirror 28 is in 5 in an enlarged manner and with a different orientation than in 1 shown and its operation is explained below. The arrow in 5 shows in the direction of the optical axis of the first beam path. The one from the step mirror 28 The reflected measuring light partial bundle and the reference light partial bundle then pass through the third beam splitter cube again 26 and hit there via detector optics 29 on a detector 30 ,

Not the third beam splitter cube 26 deflected portion of the measuring light bundle 21 . 22 as well as the reference light beam meets a flat mirror 31 , is reflected from there and from the third beam splitter cube 26 also via the detector optics 29 on the detector 30 given. In the Michelson interferometer 27 is a first beam path through the third beam splitter cube 26 , the step mirror 28 and the detector 30 Are defined. A second beam path is through the third beam splitter cube 26 , the plane mirror 31 and the detector 30 Are defined.

The optical path in the first beam path depends on where on the step mirror 28 the light is reflected. The distances of the plane mirror 31 from the beam splitter 26 and the level mirror 28 from the beam splitter 26 are chosen so that by the Mirau interferometer 18 generated difference in the optical path between the measurement light bundles on the one hand and the reference light bundles on the other hand is approximately equalized if one of the reference light sub-beams z. B. the first beam path and the associated measurement light sub-bundle passes through the second beam path. In this case, the interference path common to the first beam path and the second beam path occurs 32 on measurement interference between related reference light sub-bundles and measurement light sub-bundles. However, measurement interference is only generated by the portion of the reference light sub-bundle for which, given the short coherence length of the source light used, the compensation in the first interferometer unit 7 generated path difference to the associated measuring light beam is sufficiently accurate. This usually only applies to one at a certain measurement level 33 (please refer 5 ) of a measurement level field 7 of the step mirror 28 reflected portion. Both the measurement interference and the step level 28 are on the detector's image sensor array, not shown here 30 optically mapped. It can thus be determined which measurement level 33 the interference creates. From the known geometric conditions, the distance to be determined between the second beam splitter plate can then be determined directly 20 and the surface of the measurement object 1 be closed for a certain grid position.

In order to be able to make a clear statement about the distance to be determined, the Michelson interferometer must be calibrated 27 necessary. This is on the step mirror 28 a calibration level 34 (please refer 5 ) intended. The calibration level 34 generates a calibration path in the first beam path, which is the shortest optical path in the first beam path. The step mirror 28 and the plane mirror 31 are placed so that the distance of the reflection surface 35 the calibration level 34 from the beam splitter 26 as exactly as possible with the distance of the plane mirror 31 from the beam splitter 26 matches. The distance of the measuring stage field 7 from the reflective surface 35 the calibration level 34 and the extent of the measurement level field 7 in the direction of the optical axis of the first beam path thus defines the measuring range. All on the beam splitter 26 generated sub-bundle of the reference light bundle and the measurement light bundle 21 . 22 interfere with a sufficiently precise correspondence between the calibration path and the optical path of the second beam path in the interference path 32 together. This from the calibration level 34 The generated calibration interference thus confirms the desired geometric relationships.

From the known level of the calibration level 34 and the known step heights of the measuring steps 33 can be determined from the position of the in the interference path 32 generated measurement interference in the image in the detector 30 the optical path difference between the interfering parts of the mutually assigned reference light sub-bundle and measurement light sub-bundle and thus that in each case determine the correct distance per grid point. The surface profile of the measurement object thus results across all grid points. At the detector 30 is a color-sensitive CCD camera, so that the different measuring light beams 21 . 22 can be evaluated at the same time.

It is advantageous to use the step level 28 around a first beam path to the optical axis and to the surface normal of the mirror surfaces of the stepped mirror 28 vertical tilt axis. Due to the given width of the calibration level 34 With the inclination, a calibration area containing the calibration path is created. This can result in displacements of the stepped mirror due to mechanical or thermal influences 28 can be determined by the calibration interference in the optical image in the detector 30 on the reflective surface 35 the calibration level 34 shifts. If such a shift is found, the step level needs 28 not to be repositioned with mechanical aids. Rather, the shift can be determined by means of image processing and can be incorporated into the calculation of the respective distance to be determined. It is thus possible to make displacements or changes in the position of the step mirror even during a measurement 28 to determine and to consider for the determination of the measurement result.

In the 6 to 8th is the detector optics 29 explained in more detail.

In 6 is the detector 30 pictured, which is there on a in 1 circuit board not shown 35 located. On the board 35 is in screw holes 36 countersunk screws, not shown here, a housing bracket 37 fixed. A housing 38 is in a cylindrical passage of the housing bracket 37 in the direction perpendicular to the board 35 guided. The housing 38 can by means of a fixing screw 39 be fixed.

8th shows a sectional oblique view of the housing 38 , In the case 38 is a lens holder 40 arranged on the two rod lenses 41 are fixed. If the housing 38 on the cover slip of the detector 30 ( 6 ) is lowered, the lens holder is supported 40 immediately on this cover slip and is against an elastic compensation ring 42 pressed, which in turn is on an edge serving as a support element 43 in the wall of the housing 38 supported.

By fixing the housing bracket 37 on the board 35 is the longitudinal axis of the bushing in the housing bracket 37 and thus the longitudinal axis of the housing 38 perpendicular to the plane of the board 35 aligned. Due to manufacturing tolerances, the detector chip 30 and with that to the detector chip 30 usually cover glass parallel to the plane of the board 35 be tilted. Through the elastic compensation ring 42 this tilt is absorbed so that when the housing is fixed 38 the lens holder 40 and with it the lenses 41 parallel to the detector chip 30 remains aligned.

By turning the housing 38 the rod lenses can about its longitudinal axis 41 parallel to the sensor lines of the detector chip, which are not shown separately here 30 aligned so that from each rod lens 41 the radiation is focused on, for example, exactly one specific sensor line. The readout process can be limited to the sensor lines exposed to the focused radiation, so that high measuring frequencies are possible.

7 shows an alternative form of training in detector optics 29 in a lateral cross section. Corresponding elements are the 6 to 8th provided with the same reference numerals. So is the housing bracket here 37 on the board 35 fixed. As an alternative to fastening with screws, the housing bracket can be used 37 for example, also be glued on. In the housing bracket 37 is the housing 38 with a cylindrical shape, in which the lens holder 40 with one or more rod lenses 41 is arranged. Depending on the optics chosen, it may be necessary to go to the detector chip 30 keep a certain distance. Because of this is a cylindrical spacer 44 provided, which is directly on the cover slip of the detector chip 30 supported. When lowering the housing 38 becomes the lens holder 40 over the edge 43 and the balance ring 42 on the spacer 44 supported. It is possible to use lens holder 40 and spacers 44 to train in one storey.

In all exemplary embodiments of the detector optics 29 can in the housing 38 or in front of the housing 38 further optical elements, not shown in the figures, such as a converging lens, can be provided, which interact with the lenses arranged in the housing 41 produce the desired effects.

3 shows an encoding plate as an alternative to the color-based coding of the source light 45 whose permeability increases in one direction for the radiation used. This is in 3 indicated by the decreasing density of the lines drawn. 4 shows the permeability of the coding plate as a function of its longitudinal extent. The coding is done here by means of the intensity differences between different source beam bundles. The one on the detector 30 Interferences identified can be assigned to the associated source beam bundles on the basis of their intensity differences.

1

measurement object

2

light source

3

coupling optics

4

supply fiber

5

expansion optics

6

Source light beam

7

Measuring levels of field

8th

Beam splitter cube

9

DMD unit

10

coding plate

11

Farbcodierplatte

12 until 14

zones the color coding plate

15 until 16

Source light beam

17

second Beam splitter cube

18

Mirau interferometer

19

Beam splitter plate

20

Beam splitter plate

21

Measuring light beam

22

Measuring light beam

23

second coupling optics

24

Optical fiber cable

25

second expansion optics

26

third Beam splitter cube

27

Michelson interferometer

28

stepped mirror

29

detector optics

30

detector

31

mirror

32

Interterenzstrecke

33

measuring stage

34

calibration stage

35

circuit board

36

screw

37

housing support

38

casing

39

fixing screw

40

lens holder

41

rod lens

42

compensation ring

43

edge

44

spacer

45

coding plate

Claims (24)

Method for the interferometric examination of a measurement object ( 1 ), in which a) a spatial light modulator having a plurality of individually switchable and / or controllable modulator elements ( 9 ) is illuminated areally with incoherent or short-coherent source light, at least two parts of the source light being coded in different ways and each differently coded part being a different area of the spatial light modulator ( 9 ) areally illuminated, b) a separate source light bundle is formed from each differently coded portion of the source light by means of the modulator elements and into a first interferometer unit ( 18 ) is coupled in, c) in the first interferometer unit each source light bundle in each case into a measurement light bundle ( 21 . 22 ) and an associated reference light beam is divided, d) the measurement light beam ( 21 . 22 ) are scanned across the surface of the measurement object to be examined, e) the measurement light bundles reflected by the measurement object surface ( 21 . 22 ) and the associated reference light bundles of a second interferometer unit ( 27 ) are fed, f) in the second interferometer unit ( 27 ) Percentage of each measuring light beam ( 21 . 22 ) superimposed with parts of the associated reference light bundle after passing through different optical paths and any interferences occurring in association with the respective optical path are determined, and g) the optical paths covered by the interfering parts of the measuring light and the associated reference light in the second interferometer unit according to the codings can be evaluated separately. A method according to claim 1, characterized in that as a spatial light modulator ( 9 ) a digital mirror device (DMD) is used. A method according to claim 1, characterized in that as a spatial light modulator ( 9 ) a liquid crystal display (LCD) is used. Method according to one of claims 1 to 3, characterized in that that color coding is used by the source light in at least two parts with different wavelengths or different Wavelength ranges is divided. Method according to one of claims 1 to 3, characterized in that that an intensity coding is used by the source light in at least two parts with different intensity values is divided. Method according to one of claims 1 to 5, characterized in that the surface topography of the measurement object ( 1 ) is determined. Method according to one of claims 1 to 5, characterized in that a three-dimensional depth profile of the measurement object ( 1 ) is determined. Method according to one of claims 1 to 7, characterized in that a) each measuring light beam ( 21 . 22 ) and each reference light beam in the second interferometer unit ( 27 ) in a first and a second sub-bundle is divided, b) each first measurement light sub-bundle and each first reference light sub-bundle passes through a first beam path and thereby on at least one measurement stage field ( 7 ) step body ( 28 ) is reflected, the optical path in the first beam path from the location of the reflection on the step body ( 28 ) depends, c) a second beam path of the second interferometer unit every second measuring light partial bundle and every second reference light partial bundle ( 27 ) passes through, d) all sub-bundles to one detector ( 30 ) are fed to the interference path common to both beam paths at the end ( 32 ), e) the steps ( 33 ) of the at least one measuring level field ( 7 ) optically on an image sensor field of the detector ( 30 ) are mapped and g) the position of the images of measurement interferences occurring between each measurement light sub-bundle and the associated reference light sub-bundle in the image of the measurement stage field ( 7 ) on the detector ( 30 ) is used for the measurement. A method according to claim 8, characterized in that a) the step body ( 28 ) is arranged in such a way that a reflection of the reflecting surface ( 35 ) a calibration level ( 34 ) the optical calibration path generated in the first beam path exactly matches the optical path in the second beam path, b) the calibration stage ( 34 ) also optically on the image sensor field of the detector ( 30 ) is mapped and c) the calibration interferences generated by the respective superimposition of the measuring light partial bundles with the associated reference light partial bundles when passing through the calibration path and the second beam path in the interference path to check the position of the step body ( 28 ) are determined. A method according to claim 8 or 9, characterized in that the step body ( 28 ) is arranged such that the surface normals of the reflection surfaces ( 35 ) the calibration level ( 34 ) and / or the steps ( 33 ) of the measuring level field ( 7 ) are inclined to the optical axis of the first beam path, and the position of the calibration interference in the image of the reflection surface ( 35 ) the calibration level ( 34 ) on the detector ( 30 ) is determined and used to calibrate the measurement result. Method according to one of claims 8 to 10, characterized in that the calibration stage ( 34 ) and / or the levels ( 33 ) of the measuring level field ( 7 ) individually and in each case by means of separate optical means on one or two mutually adjacent image sensor lines. A method according to claim 11, characterized in that as separate optical means rod lenses ( 41 ) be used. A method according to claim 11 or 12, characterized in that only the image sensor lines are read, on the steps ( 33 . 34 ) of the step body ( 28 ) are mapped. Device for the interferometric examination of a measurement object, comprising a) at least one light source emitting incoherent or short-coherent source light ( 2 ), b) a source light in reference light and measuring light ( 21 . 22 ) dividing first interferometer unit ( 18 ) and c) means for coupling the object ( 1 ) reflected measuring light ( 21 . 22 ) and the reference light into a second interterometer unit ( 27 ) and a detector ( 30 ) evaluation device, characterized by d) a coding unit ( 10 ) with at least two coding areas separated from each other ( 12 . 13 . 14 ) for coding the source light e) seen in the beam direction of the source light behind the coding unit ( 10 ) and before the first interferometer unit ( 18 ) a spatial light modulator that can be illuminated in different areas by the differently coded source light ( 9 ) with a large number of individually switchable and / or controllable modulator elements with which at least two differently coded differently coded source light bundles can be generated in a controlled manner, and f) an evaluation device for evaluation separated by coding. Device according to claim 14, characterized in that the coding unit ( 10 ) a color filter unit ( 11 ) with at least two filter areas that are separated from one another over a surface and are permeable to different wavelengths or wavelength ranges. Device according to claim 15, characterized in that the detector ( 30 ) includes a digital color camera. Device according to claim 14, characterized in that the coding unit ( 10 ) an intensity filter unit ( 45 ) with at least two flatly separated intensity filter areas with different intensity transmittance for the light used. Device according to one of claims 14 to 17, characterized in that a) the second interferometer unit ( 27 ) aa) means for dividing each in the first interferometer unit from the differently coded source light bundles and into the second interfer rometer unit ( 27 ) incoming reference light beam and measuring light beam ( 21 . 22 ) in each case two sub-bundles, one of which passes through a first beam path and the other through a second beam path, bb) at least one measuring stage field arranged in the first beam path ( 7 ) step body ( 28 ), the optical path in the first beam path from the location of the reflection on the step body ( 28 ) depends, and cc) an interference path common to the first beam path and the second beam path ( 32 ) on which the sub-bundles are superimposed on one another and b) means ( 29 ) to visualize the steps ( 33 ) of the step body ( 28 ) to an image sensor field of the detector suitable for spatially resolved detection ( 30 ) are provided. Apparatus according to claim 18, characterized by one of a calibration stage ( 34 ) of the step body ( 28 ) determined calibration path in the first beam path of the second interferometer unit ( 27 ), whereby the length of the calibration path corresponds exactly to the optical path in the second beam path. Device according to claim 19, characterized in that the step body ( 28 ) is arranged such that the surface normal of the reflection surface ( 35 ) at least the calibration level ( 34 ) is inclined to the optical axis of the first beam path. Device according to claim 19 or 20, characterized in that the second interferometer unit ( 27 ) includes a Michelson interferometer and the step body ( 28 ) is a mirror with a stepped reflective surface. Device according to one of claims 18 to 21, characterized in that the first interferometer unit ( 18 ) is a Mirau interferometer. Device according to one of claims 18 to 22, characterized in that the means ( 29 ) for the optical imaging of the at least one measuring stage field ( 7 ) and the calibration level ( 34 ) comprise several independent imaging devices, each of which comprises the calibration level ( 34 ) and / or the levels ( 33 ) of the at least one measuring level field ( 7 ) map individually to one or two adjacent image sensor lines. Device according to claim 23, characterized in that the optical devices rod lenses ( 41 ) are.