DE102005042733B3 - Interferometric method e.g. for recording of separation and form and optical coherence tomography (OCT), involves having multi-wavelength source or tunable source and imaging on receiver by focusing systems - Google Patents

Abstract

The method involves having a multi-wavelength source or a tunable source and imaging on a receiver by focusing systems. Chromatic depth resolution is achieved in the focusing system by a diffractive optical zone lens and a spectral analysis is carried out by a dispersive spectrometer. The interfering electromagnetic radiation is detected by a wavelength determination and the z-position of the object details determined from the spectrum such as with FFT from the knowledge of the depth resolution in the chromatic confocal system and the refractive index. An independent claim is included for an arrangement.

Description

It here is excerpts the state of spectral interferometry means Two-beam interferometry cited in which case the chromatic depth splitting in particular at Application of a Mirau interferometer is relevant.

One Approach to spectral interferometry can be found in Hege, G: Speckleverfahren for distance measurement, dissertation, in reports from the institute for technical Look. Vol. 4. 1984, pp. 20-25 [1]. However, there may be problems with objects with greater depth with the depth of field in observation or detection with high-aperture optics.

In the publication "Dispersive interferometric profilometer "by J. Schwider and L. Zhou in Opt. Lett., Vol. 19. No 13, 1994 [2] an interferometric system is described which is a Fizeau interferometer and a spectrometer linked. The interference signal is spectrally using a grid split up so that Müllersche Strips, also known as Tolansky strips, in the receiver plane can be observed. However, here is the depth measuring range through the numerical aperture limited to the object image. The object lighting with a plan Wavefront leads to a non-optimal illumination of the object and to a lesser extent lateral resolution.

A different possibility, in microscopic spectral interferometry without moving focus on mechanical parts and the depth range to was extended with the wavelength-to-depth-encoding technique of G. Li, P.-Ch. Sun, P.C. Lin and Y. Feinman in Optics Letters, 15. Oct. 2000, Vol. 20, pp 1505 to 1507 [3] with a diffractive Lens in the object beam path for chromatic depth splitting of the object bundle proposed in connection with a tunable laser. in this connection the measurement setup used requires a lot of components and is difficult to adjust.

In the publication by Peter Hlubina: "Measuring distances and displacements using dispersive white-light spectral interferometry "in SPIE 5144, pp. 628-636 [4] an arrangement for measuring distances is shown. It will by dispersion in one arm of a white light interferometer, wherein the optical path difference is not zero, a spectrally evaluable Signal generated. However, with such an approach rather only a small depth measuring range achievable.

In the publication "Accurate fiber-optic sensor for measurement of distance based on white-light interferometry with dispersion "of Pavel Pavlicek and Gerd Häusler in ICO Tokyo, paper no. 15B3-1 from 15.7.2004 [5] becomes an arrangement described in which in a fiber in the reference arm of an interferometer by means of a dispersion over the wavenumber is intensity modulated Signal is generated. However, the object distance can only be within the wave-optical depth of field of the sensor head, through the numerical aperture of the lens is limited, can be determined and is thus in particular for one high numerical aperture very limited.

in the Subject "Spectral interference Mirau microscope "by Mehta, D., S .; Saito, S .; Hinosugi, H .; Takeda, M. and Kurokawa, T. in Applied Optics, Vol. 7, March 1, 2003, pages 1296 to 1305 (6) describes a method in which at the expense of the lateral resolution the measuring field size is increased. It will be a relatively big one Depth measuring range with submicrometer depth resolution achieved. In the described Arrangement must for the realization of the measuring function acousto-optic, tunable filters are used, but they are quite expensive. This poses thus no technical solution for one inexpensive Sensor dar.

in the Technical Paper "Spatio-spectral digital holography for full-field tomographic imaging with adaptive focusing "by M. Pawlowski, Y. Sakano, Y. Miyamoto, M. Takeda and K. Obayashi in Proc. Of SPIE Vol. 5531 (7), pages 121 to 126 becomes a holographic process described in the object information outside the focus depth at The microscopic image can be adaptively reconstructed numerically by monochromatic waves are propagated. It is for 3D capture An object does not require mechanical scanning. Also in this Arrangement must for the realization of the measuring function also acousto-optic, tunable Filters are used.

In the published patent application DE 10321895 A1 (8) "Interferometric sensor for chromatic object depth scanning" by K. Körner and W. Osten is introduced in a spectral interferometer in the Fourier plane of the associated imaging system, a spectrally refractive index variable element which the desired chromatic longitudinal splitting or depth splitting of the object beam in It also describes the use of a Mirau interferometer with compensation of the chromatic depth splitting by means of chromatic refractive power in the reference beam path.

The mechanical accessibility of the Fourier plane is especially for high-aperture microscope objectives, the one for Mirau interferometer be set, but not always given. However, it is essential that in the prior art in a Mirau interferometer with a numerical aperture of 0.55, for example, diffraction-limited imaging for both reference and object bundles is difficult to achieve if both a chromatic depth splitting in the object space of, for example, 20 μm, as well as an optical path difference in the interferometer of, for example, only 5 .mu.m to 50 .mu.m, should be achieved in order to achieve a sufficiently low spatial frequency of the Müller strips for the problem-free evaluation.

In the publication by E. Papastathopoulos, K. Körner and W. East "Chromatic Confocal Spectral Interferometry ", Proceedings of Fringe 2005, editor W. Osten, Stuttgart, Springerverlag 2005 (9), this paper will be published on 11 September 2005 the method of spectral interferometry with chromatic depth splitting of the object bundle shown in the object space using the example of a Linnik interferometer. The Linnik interferometer allows by the application of a second imaging system for the reference beam path the setting of a sufficiently small optical path difference, including the Zero gait difference by sharing the second imaging system is moved with the reference mirror for adjustment. It can the optical in the field then occurring as a result of this shift Gait variation by Haidinger rings numerically if required Getting corrected. The Linnik interferometer However, it is inherently quite complex, bulky and difficult to adjust and thus more for Applications in the measuring laboratory suitable.

field of use the invention

The Invention for spectral two-beam interferometry with chromatic Depth splitting can for diverse Tasks in the interferometric technique, in particular for testing and detection tasks be used. In particular, the following applications for the invention Proposed: Optical Coherence Tomography (OCT), Optical Coherence Microscopy (OCM) for biological and technical applications, acquisition of depth profile, refractive index profile, the optical thickness, the layer thickness and the reflectivity of a Object. Furthermore, the inventive solution also for optical data readout be used by the magnitude of the intensity of the Pits and lands of a data carrying layer of an optical disk returning radiation is detected.

Farther can be moved laterally by application of the invention the distance Objects are detected as well as defects on technical surfaces, such as Cracks, constrictions and microholes in welds, due the change the object depth in the area of a defect can be detected quickly.

The Invention can also for the detection of the distance, the profile, the microform or the refractive index of biological samples, used for example in biological cavities become. It can also be used with immersion techniques.

Goals of invention

The The aim of the present invention is to provide something new for the commercial To provide application.

The technical aim of the invention is to increase the flexibility in terms the positioning of the depth of the usable depth measuring range in Object space as well as the enlargement of the depth the usable depth measuring range, in particular when using an imaging system with a comparatively high numerical Aperture, for example in the range of 0.4 to 0.8.

Especially should also be a simple, relatively robust and cost-effective one-point sensor built can be without the need for mechanical scanning in the object space. In particular, very cost-effective, fiber-coupled spectrometer should and fiber-coupled superluminescent diodes are used can.

One Another object of the invention is, by the application of inventive teaching a substantial miniaturization of the sensor head compared to the Linnik interferometer, also for example the sensor for Use in minimally invasive medicine or in borehole inspection to make applicable.

The with the inventive sensor when measuring optical signals obtained should be using radiation detector or rastered radiation detector like a line or area camera become. Instead of a spectrometer is also a tunable Light source can be used.

Task of invention

By optically probing the surface of the object in different depths of the object space, optical signals are obtained from these depths without the mechanical movement of components - especially in the object space - are obtained. In this case, an at least approximately diffraction-limited lateral imaging of the object is to take place by means of an imaging system with a comparatively high numerical aperture, which is also penetrated by reference radiation. It is therefore an inventive arrangement without application of a second imaging system for reference radiation can be constructed.

In order to the inventive task is to be solved for spectral Two-beam interferometer with chromatic depth splitting for Magnification of the Depth measuring range with an imaging system for the object, the imaging system for spectral broadband radiation is designed and which at the same time is traversed by reference radiation, the setting of a sufficiently small allow optical path difference. Here is also the optical retrace zero included. This should also be the case comparatively large Chromatic depth splitting can be achieved. Especially should this task also for a Mirau interferometer can be solved but also for example for a Michelson, Twyman-Green or a Mach-Zehnder interferometer can be applied.

This means for the inventive task in detail that the distance z _{i of} a sharply imaged object point P _i in the depth measuring range Δz_c, which is given by chromatic depth splitting in the imaging beam path for object bundles, is to be set from the surface (G) of the same optical path difference in the object space. that there is a sufficiently small optical retardation in the two-beam interferometer, which leads to Müllerian stripes in a spectrometer, which are technically well evaluated in terms of their frequency over the wavelength.

on the other hand should during the wavelength scan using a temporally tunable, monochromatic radiation source solved the inventive task be that electromagnetic interference modulations over the Time can be generated, which is a sufficiently small and therefore technically have good evaluable frequency. This innovative task especially for solved a Mirau interferometer which, by its simplicity, can be comparatively low volume and also its high stability and robustness in many Applications has already taken a firm place. It will the trend towards the use of the Mirau interferometer as optical, more compact sensor in the future.

description the invention based on the features

The object of the invention is achieved with the following inventive features:
It is a method for spectral two-beam interferometry with chromatic depth splitting in the object beam path by a chromatic power
proposed for testing of an object or for reading an optical disk. The optical data carrier then represents the object. The spectral two-beam interferometer is constructed as follows: With a reference beam path and a reference reflector and with the object beam path, which is traversed by at least one object sub-beam, with at least partial imaging of the object or at least one object point by means of object partial beams by at least one imaging system, which is usually at least approximately diffraction-limited and usually has a comparatively large refractive power, which represents the main power in the arrangement. The imaging system is always interspersed with reference radiation. The method is practiced using at least one source of electromagnetic radiation and at least one detector, or a rasterized electromagnetic radiation detector and at least one spectrometer or wavelength-tunable source of electromagnetic radiation. In this case, the object beam path represents the range from the beam splitting to the object and back to the beam splitting, and the reference beam path is the range from the beam splitting to the reference reflector and back to the beam splitting.

• a) entweder eine zumindest näherungsweise achromatische Nebenbrechkraft in den Referenzstrahlengang durch ein strahlenfokussierendes oder strahlendivergierendes Referenzelement oder Referenzsystem eingeführt, wobei die Nebenbrechkraft hier als Referenz-Nebenbrechkraft bezeichnet wird, wobei die achromatische Referenz-Nebenbrechkraft das gleiche Vorzeichen wie die chromatische Brechkraft im Objektstrahlengang aufweist.

Main method feature (1): According to the invention

• a) introduced either an at least approximately achromatic secondary refractive power in the reference beam path through a beam-focusing or radiant-diverging reference element or reference system, wherein the secondary power is referred to herein as the reference power, wherein the achromatic reference power has the same sign as the chromatic power in the object beam path.

• b) eine zumindest näherungsweise achromatische Nebenbrechkraft in den Objektstrahlengang durch ein strahlenfokussierendes oder strahlendivergierendes Element oder System eingeführt, wobei die Nebenbrechkraft hier als Objekt-Nebenbrechkraft bezeichnet wird, wobei die achromatische Objekt-Nebenbrechkraft das umgekehrte Vorzeichen wie die chromatische Brechkraft im Objektstrahlengang aufweist.

Or, it will be according to the invention

• b) introducing an at least approximately achromatic secondary refractive power into the object beam path through a beam-focusing or beam diverging element or system, wherein the secondary power is referred to herein as an object power, wherein the achromatic object power has the opposite sign as the chromatic power in the object beam path.

• c) sowohl eine zumindest näherungsweise achromatische Nebenbrechkraft in den Referenzstrahlengang durch ein strahlenfokussierendes oder strahlendivergierendes Referenzelement oder Referenzsystem als auch eine zumindest näherungsweise achromatische Nebenbrechkraft im Objektstrahlengang durch ein strahlenfokussierendes oder strahlendivergierendes Element oder System eingeführt, wobei die Wirkung der eingesetzten Elemente oder Systeme eine resultierende achromatische Nebenbrechkraft ergibt, mittels welcher der Betrag des Abstandes z von einem Objektpunkt P im Tiefenmessbereich zur Fläche G gleichen optischen Gangunterschiedes verkleinert wird.

Or else, it will be according to the invention

• c) introducing both an at least approximately achromatic secondary refractive power into the reference beam path through a beam-focusing or beam-diverging reference element or reference system and an at least approximately achromatic secondary power in the object beam path through a beam-focusing or beam-diverging element or system, the effect of the elements or systems employed being a resulting achromatic out-of-focus power results, by means of which the amount of the distance z from an object point P in the depth measuring range to the surface G same optical path difference is reduced.

Thus, the distance z _{i of} a sharply imaged object point P _i in the depth measuring range .DELTA.z_c from the surface (G) same optical path difference in the object space can be set so that a sufficiently small optical retardation z _i in the two-beam interferometer, the Müller's stripes in a Spectrometer leads that are technically well evaluated in terms of their frequency over the wavelength. The depth measuring range Δz_c is given by the chromatic depth splitting in the imaging beam path for object bundles. In this case, the achromatic Nebenbrechkraft is rather low compared to the main power and is preferably only a few percent of the same. In this case, a part of the main refractive power of the imaging system can be co-used to generate the secondary power by lenses are preferably irradiated several times.

On the detector produces an intensity variation in the method, a spectrum of intensity over the Wavenumber, which the well-known Müller's stripes, also as Tolansky strip denotes. The acquisition of the measurand, for example the object distance takes place by means of the evaluation of Müller's Strip, because their frequency, or their phase rise above the Wavelength or its maximum of the envelope also of the optical Path difference in the two-beam interferometer is dependent. The frequency, the phase rise above the Wavelength and the position of the maximum of the envelope are correlated with the measured variable. The way of evaluating the Mueller strip to the Measured variable or Obtaining the measurement information is not inventive in this document Object. It should be noted, however, that the introduction of the chromatic depth splitting a significant irregularity of the modulation frequency, a chirp in the interference wavelet. The visibility of the effect depends doing both of the strength the chromatic splitting off as well as the diameter of the Confocal aperture, or in the case of fiber coupling also of the fiber diameter). Despite this deviation, the evaluation the object position by the calculation of the carrier frequency of the interference pattern with the equation dφ / dω = 2z / c. For the numerical description of Müller's Stripes see also [3] - [5] and [9].

on the other hand can in a wavelength scan by means of a monochromatic radiation source electromagnetic Interference modulations via the time to be generated, which is a technically well-evaluated frequency exhibit. This can be done in particular for a Mirau interferometer.

feature 2: Furthermore, according to the invention in the Method for spectral two-beam interferometry with chromatic depth splitting preferably the chromatic refractive power in the object beam path the reference Nebenbrechkraft at least partially compensated or possibly overcompensated.

With these features, it is possible to set the distance z _i to a sharply imaged object point P _i with respect to the position of the point OPD_0 same optical path difference in the object space that an optical retardation z _{i is} in the two-beam interferometer, the Mullerian stripes leads, which are well evaluated in terms of their frequency over the wavelength by means of spectrometer. This is the case if the spatial frequency of the Müllerian stripes can be well matched to the lateral resolution of the rasterized detector. Thus, the point OPD_0 between beam splitting and depth measuring range, outside of the depth measuring range or in the middle of the depth measuring range can be set by the choice of the reference Nebenbrechkraft.

feature 3: Furthermore, according to the invention in the Method for spectral two-beam interferometry with chromatic depth splitting preferably by the at least approximately achromatic Object-Nebenbrechkraft the longitudinal chromatic aberration in the object beam path by at least one radiation-focusing or radiative-diverging one and at least approximately achromatic Element or system at least partially compensated or overcompensated. Thus, the spatial frequency to the lateral resolution of the rasterized detector be well adjusted.

Feature 4: Furthermore, according to the invention in the method for spectral two-beam interferometry with chromatic depth splitting, preferably by a chromatic design of the common imaging system with adapted chromatic transverse aberration, the chromatic Queraberration for the object sub-beam, which may be present in the object beam path undesirably, made at least approximately zero. Thus, an object field without chromatic transverse aberration can be imaged and the magnification is at least approximately constant for the wavelengths of the radiation used.

Farther can in the method for spectral two-beam interferometry with chromatic depth splitting preferably in the imaging beam path existing chromatic longitudinal split compensated by means of at least one chromatic element in the reference arm become. Thus, an achromatic reference beam path can be reached.

there it is necessary, both in the image via the reference beam path as well as over the Object beam the spherical Aberration, so the opening error, sufficiently well to correct, so that at least approximately Diffraction-limited imaging by means of radiation beam from both beam paths done can.

Arrangement: Spectral two-beam interferometer arrangement with chromatic depth splitting in the object beam path by a chromatic refractive power by means of at least one beam-focusing or radiating divergent chromatic element or system with chromatic element
for testing an object or for reading an optical data carrier, which then represents the object, with at least one light source and with at least one rastered detector of electromagnetic radiation, a beam splitter surface and at least one spectrometer and with object and reference beam path and a reference reflector in the same and a Object imaging system that represents the main power of the optical assembly.

• a) im Referenzstrahlengang eine zumindest näherungsweise achromatische, strahlenfokussierende oder strahlendivergierende Linsenfläche, oder Linse, oder Linsengruppe, oder ein Spiegel, oder eine Spiegelgruppe, oder eine Spiegellinse, oder eine Komponente also jeweils mit positiver oder mit negativer Brechkraft, der Referenz-Nebenbrechkraft, angeordnet, wobei die achromatische Referenz-Nebenbrechkraft das gleiche Vorzeichen wie die chromatische Brechkraft des strahlenfokussierenden oder strahlendivergierenden chromatischen Elements oder Systems im Objektstrahlengang aufweist.
• b) Oder es ist im Objektstrahlengang eine zumindest näherungsweise achromatische, strahlenfokussierende oder strahlendivergierende Linsenfläche, oder Linse, oder Linsengruppe, oder ein Spiegel, oder eine Spiegelgruppe, oder eine Spiegellinse oder eine Komponente also jeweils mit positiver oder negativer Brechkraft, der Objekt-Nebenbrechkraft, angeordnet, wobei die achromatische Objekt-Nebenbrechkraft das umgekehrte Vorzeichen wie die chromatische Brechkraft des strahlenfokussierenden oder strahlendivergierenden chromatischen Elements oder Systems im Objektstrahlengang aufweist.
• c) Oder es ist sowohl im Referenzstrahlengang als auch im Objektstrahlengang eine zumindest näherungsweise achromatische, strahlenfokussierende oder strahlendivergierende Linsenfläche, oder Linse, oder Linsengruppe, oder Spiegel, oder Spiegellinse, oder Komponente also jeweils mit positiver und/oder negativer Brechkraft angeordnet, wobei die Wirkung der eingesetzten Komponenten eine resultierende achromatische Nebenbrechkraft ergibt, mittels welcher der Betrag des Abstandes z_i von einem scharf abgebildeten Objektpunkt P_i im Tiefenmessbereich zur Fläche G gleichen optischen Gangunterschiedes verkleinert wird. Dabei ist auch die Wirkung einer dispersiven Platte oder eines Umlenkprismas jeweils im Objektstrahlengang in den Abgleich des optischen Gangunterschiedes und der Auslegung der chromatisch und weitgehend achromatischen Brechkräfte einzubeziehen. Im Fall eines optimalen Abgleichs mit dem Ergebnis eines hinreichend kleinen optischen Gangunterschiedes können Müllersche Streifen auf dem Detektor optimal ausgewertet werden, da so die Ortsfrequenz an die laterale Auflösung des gerasterten Detektors gut angepasst werden kann. Die achromatische, strahlenfokussierende oder strahlendivergierende Komponente, beispielsweise auch eine Spiegellinse, weist dabei im Vergleich zum Abbildungssystem für das Objekt, welches ja die Hauptbrechkraft der optischen Anordnung darstellt, eine eher deutlich geringere Brechkraft auf.

Arrangement main feature (5): According to the invention

• a) in the reference beam path, an at least approximately achromatic, radiation-focusing or radiant diverging lens surface, or lens, or lens group, or a mirror, or a mirror group, or a mirror lens, or a component thus each with positive or negative refractive power, the reference power, arranged wherein the reference achromatic refractive power has the same sign as the chromatic refractive power of the beam focusing or beam diverging chromatic element or system in the object beam path.
• b) Or it is in the object beam path an at least approximately achromatic, radiation-focusing or radiating divergent lens surface, or lens, or lens group, or a mirror, or a mirror group, or a mirror lens or component so each with positive or negative refractive power, the object power, wherein the achromatic object-off power has the opposite sign as the chromatic power of the radiation-focusing or radiating divergent chromatic element or system in the object beam path.
• c) Or it is both in the reference beam path and in the object beam path an at least approximately achromatic, radiation-focusing or radiating divergent lens surface, or lens, or lens group, or mirror, or mirror lens, or component thus each arranged with positive and / or negative refractive power, the effect The components used a resulting achromatic Nebenbrechkraft results, by means of which the amount of the distance z _i from a sharply imaged object point P _i in the depth measuring range to the surface G same optical path difference is reduced. In this case, the effect of a dispersive plate or a deflecting prism in each case in the object beam path in the adjustment of the optical path difference and the interpretation of the chromatic and largely achromatic powers must be included. In the case of an optimal alignment with the result of a sufficiently small optical path difference, Müllerian stripes can be optimally evaluated on the detector since the spatial frequency can thus be well adapted to the lateral resolution of the rastered detector. The achromatic, radiation-focusing or radiatively diverging component, for example, a mirror lens, in this case, in comparison to the imaging system for the object, which indeed represents the main power of the optical arrangement, a rather much lower refractive power.

The achromatic, radiation-focusing or radiative-diverging Component may also be referred to as achromatized diffractive Zone lens or zone lens group, also preferably as a hybrid refractive-diffractive doublet or diffractive multi-order Zone lens, be formed, which then in the reference beam path the Contributing breaker power.

In this case, the source of electromagnetic radiation broadband, for example in the UV, in the VIS or in the IR region, be formed and short-pulse, for example, a short-pulse laser, and its pulses with a camera which serves as a detector, for example in 100 Hz Range, be synchronized. This is for moving scenes of Advantage.

on the other hand can also be a tunable laser or a broadband White light laser be used. Furthermore, a spectrally broadband can also Source of electromagnetic radiation can be used, the one controllable monochromator is arranged to tune the wavelength.

Farther can here to enlarge the Depth measuring range also at least two monochromatic sources electromagnetic radiation of different wavelengths with Frequency modulation can be used, so that the known heterodyne method can be applied. With the radiation of each wavelength is the object is scanned at a different depth.

feature 6: continues According to the invention in the spectral two-beam interferometer arrangement with chromatic depth splitting preferably the reference power of at least 30% of the chromatic power in the object beam path for the mean wavelength of the spectral range used for the at least partial imaging of the object. Thus, the spatial frequency to the lateral resolution of the rasterized detector can be optimally adapted within wide limits.

feature 7: Furthermore, according to the invention in the spectral two-beam interferometer arrangement with chromatic depth splitting preferably in the object beam path at least one diffractive-optical, Radiation-focusing or radiant diverging zone element and in the reference beam path at least one refractive, beam-focusing or radiating divergent lens surface, lens or mirror lens or arranged a mirror surface. Furthermore, the residual chromatic aberration of the beam diverging lens surface or lens corrected by the chromatic design of the imaging system so that all foci of beams of all wavelengths used used spectrum sharply mapped on the reference reflector can be. Thus, a point A on the reference reflector at least approximately be imaged on the detector free of chromatic errors. This is one of the prerequisites that the contrast of the Mullerian Strip on the detector for the radiation used throughout the spectrum is high.

feature 8: Furthermore, according to the invention in the spectral two-beam interferometer arrangement with chromatic depth splitting preferably in the object beam path at least one diffractive-optical, Radiation-focusing or radiant diverging zone element and in the reference beam path at least one radiation-focusing or radiatively diverging achromat.

feature 9: Furthermore, according to the invention in the spectral two-beam interferometer arrangement with chromatic Depth splitting preferably from the diffractive-optical, radiation-focusing or radiant diverging zone element in the object beam path the Beam shaping properties in the positive or the negative first diffraction order or in a higher positive or negative Diffraction order each used to image the object.

there it is necessary in the arrangement at the picture over the Reference beam path as well over the object beam path the spherical aberration, so the opening error, sufficiently well to correct, so that at least approximately diffraction-limited imaging by means of radiation beam from the reference mirror as also be carried out by at least one object point by means of both beam paths can. This can preferably also by the arrangement of plane parallel plates or more aspherical Imaging elements such as lenses, mirrors or mirror lenses in one of the two or even done in both beam paths.

feature 10: Furthermore, according to the invention in the spectral two-beam interferometer arrangement with chromatic depth splitting preferably the two-beam interferometer arrangement as Mirau interferometer with at least one diffractive-optical, radiation-focusing or radiatively diverging zone element formed in the object beam path. this leads to to a particularly compact and robust sensor.

feature 11: Furthermore, according to the invention in the spectral two-beam interferometer arrangement with chromatic depth splitting preferably the zone element as a phase-zone lens for the positive and / or the formed negative first diffraction order. In the first diffraction order is to achieve a high diffraction efficiency.

feature 12: Furthermore, according to the invention in the spectral two-beam interferometer arrangement with chromatic depth splitting preferably, the phase-zone lens is designed to focus radially is and this at least one refractive lens surface or Lens with radiative divergent effect, that is a dispersion component, assigned.

This leads to the desired compensation of the chromatic refractive power, so that the shift of the focal point through the phase-zone lens is at least partially compensated by refraction and thus at the focal point of the optical path difference in the interferometer sufficiently small is done. On the other hand, however, a value can be set within wide limits for the optical path difference. This is very advantageous if a specific optical path difference is needed for the application of the heterodyne method with a frequency-modulated light source in the inventive arrangement.

feature 13: According to the invention further corresponds to the spectral two-beam interferometer arrangement with chromatic depth splitting preferably the amount of Refractive power of the refractive lens surface or lens to the amount the average power of the phase-zone lens at least approximately. this leads to to an almost complete Compensation, so for focused object points the optical path difference in the interferometer especially small, including also to zero, can be made.

feature 14: Furthermore, according to the invention in the spectral two-beam interferometer arrangement with chromatic depth splitting preferably the beam splitter surface with a curvature educated. this leads to to a particularly simple optical arrangement. In the limit case are only two optical functional surfaces arranged in the entire beam splitter assembly, which are arranged upstream of the imaging system are.

feature 15: Furthermore, according to the invention in the spectral two-beam interferometer arrangement with chromatic depth splitting preferably at least one refractive plane parallel plate in the reference and / or in the object beam path for adaptation of the dispersion in the arranged optical arrangement.

feature 16: Furthermore, according to the invention in the spectral two-beam interferometer arrangement with chromatic depth splitting preferably at least one phase zone plate in the reference and / or object beam path arranged for adjusting the dispersion in the optical arrangement. This allows it, if necessary at a large depth measuring range a slight variation of the spatial frequency of the Müllerian Adjust strip, so that in particular with a short pulse light source also moving scenes of greater depth can be detected. In this case, preferably only the maximum of the envelope of the Müllerian Strips evaluated. This can also be advantageous in conjunction with Michelson or Twyman Green interferometer. Thereby can also be a comparatively large object or a comparatively size Scene to be captured. It is possible by choosing a small illumination aperture Speckle with high contrast on the object train, which are then evaluated by camera.

feature 17: Furthermore, according to the invention in the spectral two-beam interferometer arrangement with chromatic depth splitting preferably the imaging system for the object with at least trained a Grin lens. This also leads to the illumination beam path to a very compact arrangement - especially if this too used for illustration.

feature 18: Furthermore, according to the invention in the spectral two-beam interferometer arrangement with chromatic depth splitting preferably in the imaging system at least one refractive element arranged with chromatic transverse aberration through which the chromatic Transverse aberration for the object sub-beam, the unwanted in the object beam path is present, at least approximately made to zero. Thus, an object field without chromatic Queraberration be mapped and the magnification is for the wavelength the radiation used at least approximately constant.

feature 19: Furthermore, according to the invention in the spectral two-beam interferometer arrangement with chromatic depth splitting preferably in the imaging system, at least one diffractive zone element arranged with chromatic transverse aberration through which the chromatic Transverse aberration for the object sub-beam, the unwanted in the object beam path is present, at least approximately made to zero. This also allows a magnification, the for the wavelengths of used radiation is at least approximately constant.

there is also the optical design of the optical system causes the longitudinal chromatic aberration by the interaction of the optical components upon impact of the reference bundle made the reference reflector at least approximately zero. Thus, a profile cut with good contrast of the stripes on be mapped to the spectrometer. The area coverage can also with a tunable source of electromagnetic radiation.

Feature 20: According to the invention, in the spectral two-beam interferometer arrangement with chromatic depth splitting, preferably in a Mirau interferometer, a hybrid element is arranged by means of a two-sided substrate in which a partially transparent mirror layer, which is designed as a beam splitter surface, is arranged on the substrate side assigned to the imaging system this substrate side is concave, and on the other side of the substrate, a phase-zone structure is applied with Strahlfokussierender effect in the first diffraction order. This leads to a very compact arrangement. But it can In this case also the substrate side associated with the imaging system may be formed convex and be applied to the other side of the substrate, a phase-zone structure with strahldivergierender effect in the first diffraction order. This leads to a very compact arrangement and represents an optimal arrangement, for example, for depth detection or optical data readout in one point.

feature 21: Furthermore, according to the invention in the spectral two-beam interferometer arrangement with chromatic depth splitting preferably the two-beam interferometer arrangement as Twyman-Green, Michelson or Mach-Zehnder arrangement formed. The Mach Zehnder arrangement can be used in transmitted light, with transparent objects can be examined. This is advantageously a second chromatic component to compensate for the chromatic longitudinal aberration. Of the Advantage when using a Twyman Green or the Michelson interferometer is that particularly large working distances than also object fields can be measured if the arrangement for a field corrected. In this case, the numerical aperture is clear less than the Mirau interferometer, so rather reflective surfaces or surfaces can be measured with a rather low roughness.

feature 22: Furthermore, according to the invention in the spectral two-beam interferometer arrangement with chromatic depth splitting preferably at least one confocal discriminator is arranged, which is designed so that the width of the envelope of the Müllerschen Strip optimized for the evaluation of the phase gradient is. So can unwanted Radiation are eliminated and generates an envelope for the spectrum whose center of gravity is the rough information on the Measuring object, for example, whose distance contains.

feature 23: Furthermore, according to the invention in the spectral two-beam interferometer arrangement with chromatic depth splitting preferably a microlens array, in particular for the measurement along a line or in a plane arranged. This can also be used rotating.

feature 24: Furthermore, according to the invention in the spectral two-beam interferometer arrangement with chromatic depth splitting preferably the dispersion in the overall system by means of diffraction at least a grid adjusted so that at a depth variation only a comparatively small change in the spatial frequency of Müller's stripes results. This can be done especially with a Twyman-Green interferometer with small numerical aperture with frequency evaluation of Müller's Strip a measurement range of millimeters can be achieved, for example around teeth in their shape to measure, with a confocal discrimination for the contrast can be very beneficial here.

feature 25: Furthermore, according to the invention in the spectral two-beam interferometer arrangement with chromatic depth splitting preferably a camera with logarithmic characteristic used. This is a larger range of brightness detectable on the object.

feature 26: Furthermore, in the object beam path preferably a system of electrically controllable, diffractive-optical element and an electrical steerable electrowetting lens be arranged, which the average refractive power of the diffractive optical Elements at least partially compensated. It can the degree of Chromatic depth splitting by diffractive-optical element changed be, with the readjustment of the refractive power of Elektrowetting lens the planes of sharpness and thus the position of the depth measuring range in the object space in the same depth holds. So can the width of the envelope the Müller's Changed stripes be to optimally adapt the system to the measurement task to reach. This is possible with an arrangement with immersion liquid in the Object space be beneficial.

feature 27: Furthermore, the detector may be preceded by a further two-beam interferometer be, with which by a scan of the optical path difference an analysis of the interfering radiation of the two-beam interferometer done can.

Further Features of the invention: It can be both the first positive as well as the first negative diffraction order of a diffractive optical Zone element can be used. This is preferably used for measuring range extension with a recognition of the respective diffraction order by the respective average frequency of the Müllerian Strip and the location of their intensity maximum on the wavenumber axis. It can but also bundles of objects with two different intensities or numerical apertures be achieved for optimal adaptation to the object. But it can also two depth ranges for the measurement of the distance of an object are generated simultaneously.

Farther The reference mirror can also be positioned deeper in the imaging system be, for example, at a side remote from the beam splitter surface of a Lens, which is also at least approximately can be located in the middle of the imaging system.

Farther can be the reference bundle by reflection in the zeroth diffraction order of a diffractive-optical Zone element, which acts as a beam splitter, are obtained and In this case, the diffractive-optical zone element is also applied to a curved substrate surface which, when reflected in the zeroth diffraction order, also produces an achromatic Refractive power is given and the number of required optical active surfaces can reduce.

Farther may preferably be in the object beam path of the Mirau interferometer a beam deflection, done for example by a 90 ° prism. This makes it possible interior walls to measure bores with small diameters.

Farther is in the point measurement, preferably a monitoring of the reflectivity of the object possible by the back coming intensity above that used spectral range is determined, for example by a Decoupling from coming back Radiation from the fiber in front of the spectrometer, leaving the light source dependent on can be readjusted highly dynamically by the monitor signal.

The inventive point and line sensors may preferably be highly dynamic Lateral scanners and possibly also coupled with image guides to also gain three-dimensional data from distal objects to be able to.

description the figures

The 1 is an application for a high-precision, mobile point sensor. This can be used for optical scanning of pits and lands in different deep data layers of a multilayer data carrier, but also for highly accurate distance measurement and profile measurement on a measuring machine or for testing an object at different depths, especially in a clean room environment.

The light source is a fiber-coupled superluminescent diode 1 educated. The light of the same becomes a fiber 2 coupled, passes the Y-turnout 3 and passes over the fiber piece 4 as a diverging beam on a collimator lens 5a with focal point F_5a, which serves for bundle collimation. It creates by means of this at least approximately plane waves on a microscope objective 6a , which here represents the imaging system of a Mirau interferometer, arrive, and thus be focused into the object space. The numerical aperture (NA) of the microscope objective 6a this is NA = 0.55. Between the microscope objective 6a and the object space is the beam splitter plate 7a with a convex front surface 8a on the outer plate side and the beam splitter layer 9 which is applied to the inner plate side. On the side of the beam splitter plate facing the object 7a there is a diffractive, collecting zone lens 11a , The profile depth on the diffractive, collecting zone lens 11a lies in the sublambda area. It is created by reflection at the beam splitter layer 9 a convergent reference beam R, which is at the plane reference mirror 10 is reflected. The at beam splitter plate 7a with beam splitter layer 9 passing bundles now passes in the first order, the diffractive, collecting zone lens 11a , wherein a collecting effect occurs. The effect of the zonal lens 11a In the object beam path is through the mirror lens, passing through the convex front surface 8a and the beam splitter layer 9 is formed, partially compensated. The points A and OPD_0 represent locations of the same optical path difference in the interferometer. By the wavelength-dependent refractive power of the zonal lens 11a occurs in the object space for the object bundle O_1 to a longitudinal chromatic splitting in the range .DELTA.z_c, with the Foki the short-wave radiation farthest from the beam splitter plate 7a are removed (P _λmin ). Thus, a depth scan of the object space takes place. The at a point P of a multi-layered object 12a on a layer or in another application on an object 12b Radiation reflected at a surface point P _i passes over the diffractive, collecting zone lens 11a through the beam splitter plate 7a with beam splitter layer 9 and convex surface 8a together with the reference beam R in the microscope objective 6a , Here, the transmission of the radiation takes place at the zonal lens 11a again in the first diffraction order. The refractive power of the mirror lens with the convex front surface 8a and the beam splitter layer 9 causes the focus on the planned reference level 10 is at point A and the optical path difference between the reference and the object beam at point P _i, for example, is only 35 microns. After passing the microscope objective 6a and the collimator lens 5a arise - depending on the wavelength - bundle of different wavefront curvature. The at least approximately focused in the point P _i Objektstrahlenlbündel and the reference beam, which is focused at point A, enter the end of the fiber 4 again, where P _i 'and A' represent optically conjugate points. The in the tail of the fiber 4 coupled bundles pass the switch 3 in the direction of the decoupling fiber 13 , arrive at a fiber-coupled spectrometer 14 and on a line camera 15 and are detected there. On the line camera 15 the spectrum of intensity over the wavenumber, the Müllerian stripes, arises. The evaluation can be carried out by means of the evaluation of the phase variation over the wave number, since the intensity over the wavenumber of the optical path difference in the interferometer and thus also the optical distance from the beam splitter layer 9 is dependent. The evaluation of Müller's stripes is not shown in this document.

The 2 provides an arrangement with a beam splitter plate 7a with a concave surface 8b and a radiating diverging zone lens 11b This allows a greater working distance to a measured object 12a or 12b be achieved.

The 3 Figure 4 illustrates an arrangement for a high precision, mobile point sensor with a minimum of components. This point sensor can be used to optically scan the pits and lands in different depth data layers of a multilayer data carrier 12a , but also for the distance measurement and profile measurement of an object 12b on a measuring machine or even for the examination of an object 12a at different depths, especially in a clean room environment.

The light source is a fiber-coupled superluminescent diode 1 educated. The light of the same 1 gets into a fiber 2 coupled, passes the Y-turnout 3 and passes over the fiber piece 4 as a diverging beam on a grin lens 5b with the focal point F_5b, which serves for collimation. At least approximately plane waves arise on a grin lens 6b , which here represents the imaging system of a Mirau interferometer, reach and thus be focused in the object space. Between the grin lens 6b and the object space is the beam splitter plate 7a with a concave front surface 8b and the beam splitter layer 9 pointing to the concave front surface 8b is applied. On the side of the beam splitter plate facing the object 7a there is a diffractive, radiation-collecting zone lens 11a , It is created by reflection at the beam splitter layer 9 a convergent reference beam R, which is at the plane reference mirror 10 is reflected. The at beam splitter plate 7a with the beam splitter layer 9 passing beam now passes in the first diffraction order, the diffractive, radiation-collecting zone lens 11a , The radiation-collecting effect of the zonal lens 11a is through the mirror, passing through the concave front surface 8b and the beam splitter layer 9 is formed, partially compensated. The points A and OPD_0 represent locations of the same optical path difference. By the wavelength-dependent refractive power of the zonal lens 11a occurs in the object space for the object bundle O_1 to a longitudinal chromatic splitting in the range .DELTA.z_c, with the Foki the short-wave radiation farthest from the beam splitter plate 7a are removed. Thus, a depth scan of the object space takes place. That of a point P _{i of} the multilayer object 12a reflected light passes through the diffractive, light-collecting zone lens 11a , Here, the transmission of the light takes place again in the first diffraction order, through the beam splitter plate 7a with beam splitter layer 9 together with the reference bundle R in the Grin lens 6b , After passing the grin lenses 6b and 5b arise - depending on the wavelength - bundle of different wavefront curvature. The partial bundles focused at least approximately at the point P _i enter the end piece of the fiber 4 again, pass the switch 3 in the direction of the decoupling fiber 13 , arrive at a fiber-coupled spectrometer 14 and on a line camera 15 , There the Müller stripes are formed and detected.

All 4a to 4g are designed in particular as point sensors, in each case also a confocal Dikriminierung takes place. Thus, radiation from unwanted diffraction orders at the diffractive-optical zone element 11a be eliminated, especially when the diffractive optical zone element 11a is used in both zeroth and first order. The lighting can, as in the 1 to 3 shown with the components 1 to 5a or 5b be achieved. With the components 4 . 13 to 15 the detection of Müller's stripes can be made possible.

The 4a shows an arrangement in which by means of beam splitter layer 9 the reference bundle R arises. The Lens 16a the reference bundle R focuses only very weakly. Furthermore, the usually low longitudinal chromatic aberration of the lens 16a in the imaging system 6a already corrected. The reference mirror 10 is on the lens 16a applied. For the reference beam, a part of the refractive power of the imaging system is thus used, which applies the main refractive power in the arrangement. This represents the refractive power of the lens 16a the Nebenbrechkraft the arrangement is. The Chromasie the lens 16a , in particular the longitudinal chromatic aberration, is thus due to the opposite chromasia of the rest of the imaging system 6a compensated, so that the reference beam path is achromatic with respect to the depth splitting, whereby the point A is imaged achromatisch and radiation of all wavelengths of the reference radiation, the confocal discriminator, such as the fiber 4 , happen and contribute to the training of Müller's stripes.

The 4b FIG. 12 illustrates an arrangement in which the reference beam R_0 is diffracted in the zeroth order in reflection at the diffractive optical zone element 11a is produced. The Chromasie of the lens 16a , especially their chromatic longitudinal aberration is, as in

4a described by the opposite Chromasie the rest of the imaging system 6a compensated.

The 4c FIG. 12 illustrates an arrangement in which the reference beam R_0 is also diffracted in the zeroth order in reflection at the diffractive optical zone element 11a is produced. The reference mirror 10 is even deeper in the imaging system, so even further away from the beam splitting, arranged. Here, a 90 ° prism can be integrated into the beam path to measure the inner wall of a bore.

The 4d represents an arrangement in which the reference mirror 10 on the front surface of the lens 16a is arranged. The reference beam R_0 also becomes diffracted in the zeroth order in reflection at the diffractive optical zone element 11a generated. The partial compensation of the refractive power of the diffractive-optical zone element 11a takes place by means of the concave curved surface 8b the beam splitter plate 7a , where the area 8b is thus used refractive.

In the 4e an arrangement is shown in which the surface of the beam splitter plate 7a , which faces the imaging system, is slightly concave curved. On this is the diffractive optical zone element 11a which in the first diffraction order influences the object beam in a focusing manner. The reference beam R_0 becomes in the zeroth order in reflection at the diffractive optical zone element 11c generated and experiences by the concave curved surface 8b the beam splitter plate 7a also a focus, so that a partial compensation of the chromatic power of the diffractive optical zone element 11c is given and thus reduces the distance z _i . This reduces the spatial frequency of the detected Müller stripes in the measuring range of the arrangement.

In the 4f is an arrangement for measuring the surfaces 12d represented by interiors, where the front surface 19 a 90 ° deflecting prism 20 , which faces the imaging system, is slightly convex curved. On this curved front surface 19 is the diffractive optical zone element 11d which in the first diffraction order influences the object beam in a focusing manner in transmission. By contrast, the reference bundle R_0 is in the zeroth order and in reflection at the diffractive-optical zone element 11a generated and experiences by the convex curved front surface 19 of the deflecting prism 20 a reduction of the focus, so that the path to the focal point A is geometrically extended. Thus, an at least partial compensation of the increase in the optical path difference by the optical thickness of the deflection prism 20 given in the object beam path and the reference beam path is achromatic. This results in a corresponding design of the components involved 19 . 20 11d in the measuring range of the arrangement, a sufficiently small spatial frequency of the detected Müller stripes, which can be optimally evaluated. The 90 ° deflecting prism 20 is made by externally rounded glass mounting prism 21 in a cylinder socket 22 with breakthrough 23 held. The grin lenses 5b and 6b are formed with a circular cross-section. The grin lenses 5b is fiber-coupled.

Another embodiment of an arrangement for the measurement of the surfaces 12d of interiors is based on the arrangement 4f , However, the prism is 20 executed with flat surfaces. This prism 20 are the components 7a . 7b . 8b and 11a out 2 upstream and a not shown plane-parallel compensation plate with the same Glasweglänge as the prism to compensate for the opening error.

In the 4g an arrangement is shown in which the area 8a the beam splitter plate 7a is slightly convexly curved. On this is the diffractive optical zone element 11d which in the first diffraction order influences the object beam in a focusing manner. The reference beam R_0 becomes in the zeroth order in reflection at the diffractive optical zone element 11d generated and experiences by the convex curved front surface 19 of the deflecting prism 20 a reduction in the focus of the reference beam R_0, so that the path to the focal point A is geometrically extended and the reference beam path is achromatic. Thus, an at least partial compensation of the increase in the optical path difference by the optical thickness of a water film in the object beam path in front of the object 12d with appropriate design of the components involved 8a . 7a and 11d possible. Thus, a sufficiently small spatial frequency of the detected Müllerian strip can be achieved, which is optimally evaluated.

The 5 represents an application for a highly accurate line sensor. The source of electromagnetic radiation 1b is designed as a white light laser, so spectrally broadband. The radiation of the same passes through a beam splitter 17 and a collimator lens 5a , It creates at least approximately plane waves, the lens 6a of a Mirau interferometer and by means of this lens 6a be focused in the object space. Between the lens 6a and the object space is the beam splitter plate 7a with a convex front surface 8a , On the plate 7b are the beam splitter layer 9 and the diffractive radiation-collecting zone lens 11a applied. It is created by reflection at the beam splitter layer 9 a convergent reference beam R at the reference mirror 10 is reflected. The at beam splitter layer 9 passing through beams now passes in the first order diffractive light scattering zone lens 11a , wherein the beam O_1 is formed and at the zonal lens 11a a radiation-collecting effect occurs. Due to the wavelength-dependent refractive power of the diffractive light-scattering zone lens 11a this leads in the object space for the object bundle O_1 to a longitudinal chromatic split, with the foci of the short-wave radiation being furthest away from the beam splitter assembly. Thus, a depth scan of the object space takes place. That of a point P _{i of} the object 12c reflected light passes over the zone lens 11a , Here, the transmission of the light is again in the first diffraction order, through the beam splitter layer 9 together with the reference beam R in the lens 6a of the Mirau interferometer. The refractive power of the concave front surface 9 leads to an adaptation of the optical path difference between the reference and the object beam. The reference beam R and the object beam O_1 pass through the beam splitter in transmission and form via a tube lens 18 the object 12c on a surface camera 15a which component of a line spectrometer 14b with an entrance slit 14a is. With this arrangement, a correction of the field is possible. The variation of the phase or frequency in the field is not a problem because a numerical correction of the same is easy.

6 shows an arrangement for a profile section or for flat object fields, which in the essential components 5 but does not have a spectrometer. With this arrangement, a planar measurement of the object 12c allows. This arrangement can also be used very well with an immersion imaging system for water. This is a spectrally fine tunable, tunable, narrowband laser source 1c used, so that by means of wavelength tuning of the laser source 1c the profile depth or even high-resolution the 3D microform of the object 12c by means of area camera 15a can be detected.

Claims (21)

Method for spectral two-beam interferometry with chromatic depth splitting in the object beam path through a chromatic refractive power for testing an object ( 12b . 12c ) or to read an optical data carrier, which then the object ( 12a ), with a two-beam interferometer with a reference beam path and a reference reflector and with an object beam path, which is traversed by at least one object sub-beam, with at least partial imaging of the object ( 12a . 12b . 12c ) by an imaging system ( 6a . 6b ) with a comparatively high refractive power, which represents the main refractive power in the arrangement, whereby reference radiation also passes through the imaging system, and with application of a light source ( 1a . 1b . 1c ) and a rasterized detector ( 15 . 15a ) for electromagnetic radiation and a spectrometer ( 14 . 14a ) or a wavelength-tunable source of electromagnetic radiation ( 1c ), characterized in that a) that either an at least approximately achromatic secondary refractive power is introduced into the reference beam path by a beam focusing or radiant diverging reference element or reference system, wherein the secondary power is referred to herein as the reference power, and wherein the achromatic reference power is the same sign as the has chromatic refractive power. b) or in that an at least approximately achromatic secondary refractive power is introduced into the object beam path by a beam-focusing or radiating divergent element or system, the side-power being referred to herein as object-side power, and the achromatic object-side power having the opposite sign as the chromatic power. c) or that both an at least approximately achromatic secondary refractive power is introduced into the reference beam path by a radiation-focusing or radiating divergent reference element or reference system and an at least approximately achromatic secondary refractive power in the object beam path through a radiation-focusing or radiating divergent element or system. Method for spectral two-beam interferometry with chromatic depth splitting in the object beam path through A chromatic power according to claim 1, characterized by that the chromatic power in the object beam path through the Reference secondary power at least partially compensated or overcompensated becomes. Method for spectral two-beam interferometry with chromatic depth splitting in the object beam path through A chromatic power according to claim 1, characterized by that by the object-Nebenbrechkraft the chromatic longitudinal aberration in the object beam path by at least one radiation-focusing or radiatively diverging and at least approximately achromatic Element or system at least partially compensated or overcompensated becomes. A method for spectral two-beam interferometry with chromatic depth splitting in the object beam path by a chromatic power according to at least one of claims 1 to 3, characterized in that by a chromatic formation of the common Abbildungssys Tems with adapted chromatic transverse aberration, the chromatic transverse aberration for the object sub-beam, which is present in the object beam path undesirably, at least approximately made to zero. Spectral two-beam interferometer arrangement with chromatic depth splitting in the object beam path by means of a chromatic refractive power by means of at least one beam-focusing or radiating divergent chromatic element or system with chromatic element for testing an object or reading an optical data carrier, which then represents the object, with a light source ( 1 . 1a ) and with a rastered detector ( 15 . 15a ) electromagnetic radiation, a beam splitter surface ( 9 ) and a spectrometer ( 14 . 14a ) and with object and reference beam path and a reference reflector ( 10 ) in the same and an imaging system for the object, which represents the main refractive power of the optical system, characterized by a) that either in the reference beam an at least approximately achromatic, beam-focusing or radiating divergent lens, or lens group or mirror, or mirror lens, or component so each with positive refractive power, the reference refractive power, the achromatic refractive power has the same sign as the chromatic refractive power of the beam focusing or beam diverging chromatic element or system. b) or that in the object beam path an at least approximately achromatic, beam-focusing or radiating diverging lens, or lens group, or mirror, or mirror lens, or component is thus each with positive or negative refractive power, the object-Nebenbrechkraft arranged, wherein the achromatic reference-off power has opposite sign as the chromatic power of the radiation-focusing or radiating divergent chromatic element or system. c) or that both in the reference beam path and in the object beam path an at least approximately achromatic, beam-focusing or radiating diverging lens surface, or lens, or lens group, or mirror, or mirror lens, or component is thus arranged in each case with positive and / or negative refractive power. Spectral two-beam interferometer arrangement with Chromatic depth splitting in the object beam path through a Chromatic power according to claim 5, characterized in that that the reference power of at least 30% of the chromatic Refractive power in the object beam path for the mean wavelength of the for the at least partial imaging of the object used spectral range is. Spectral two-beam interferometer arrangement with chromatic depth splitting in the object beam path by a chromatic power according to at least one of claims 5 and 6, characterized in that in the object beam path, the chromatic element as at least one diffractive-optical, radiation-focusing or radiant diverging zone element ( 11a . 11b . 11c . 11d ) is formed and in the reference beam path at least one refractive, radiation-focusing or radiating diverging lens surface ( 8a . 8b ) or lens or a mirror surface are arranged. Spectral two-beam interferometer arrangement with chromatic depth splitting in the object beam path by a chromatic refractive power according to at least one of claims 5 and 6, characterized in that in the object beam path, the chromatic element at least one diffractive-optical, radiation-focusing or radiant diverging zone element ( 11a . 11b . 11c . 11d ) and in the reference beam path at least one radiation-focusing or radiative divergent achromat are arranged. Spectral two-beam interferometer arrangement with chromatic depth splitting in the object beam path by a chromatic power according to at least one of claims 5 to 8, characterized in that the diffractive-optical, radiation-focusing or radiating divergent zone element ( 11a . 11b . 11c . 11d ) in the object beam path, the beam shaping properties in the positive or negative first diffraction order or in a higher positive or negative diffraction order are each used to image the object and the numerical aperture of the arrangement is slightly increased by the chromatic power. Spectral two-beam interferometer arrangement with chromatic depth splitting in the object beam path by a chromatic power according to at least one of claims 5 to 9, characterized in that the two-beam interferometer arrangement as Mirau interferometer with at least one diffractive-optical, radiation-focusing or radiating divergent zone element ( 11a . 11b . 11c . 11d ) is formed in the object beam path. Spectral two-beam interferometer arrangement with chromatic depth splitting in the object beam path by a chromatic power according to claim 10, characterized in that the zone element as a phase-zone lens ( 11a . 11b . 11c . 11d ) is designed for the positive and / or the negative first diffraction order. Spectral two-beam interferometer arrangement with chromatic depth splitting in the object beam path by a chromatic power according to claim 11, characterized in that the phase-zone lens ( 11a ) is designed to focus radially and this at least one refractive lens surface ( 8b ) or lens with radiant divergent effect, that is a divergent component, is assigned. Spectral two-beam interferometer arrangement with chromatic depth splitting in the object beam path by a chromatic power according to claim 12, characterized in that the amount of refractive power of the refractive lens surface ( 8b ) or the lens the amount of the average power of the phase-zone lens ( 11b ) at least approximately corresponds. Spectral two-beam interferometer arrangement with chromatic depth splitting in the object beam path by a chromatic power according to at least one of claims 5 to 13, characterized in that the beam splitter surface ( 9 ) is formed with a curvature. Spectral two-beam interferometer arrangement with Chromatic depth splitting in the object beam path through a Chromatic refractive power according to at least one of claims 5 to 14, characterized in that at least one refractive plane parallel plate in the reference and / or object beam path for adaptation of the dispersion is arranged in the optical arrangement. Spectral two-beam interferometer arrangement with Chromatic depth splitting in the object beam path through a Chromatic refractive power according to at least one of claims 5 to 15, characterized in that at least one phase zone plate in the reference and / or object beam path for adaptation of the dispersion is arranged in the optical arrangement. Spectral two-beam interferometer arrangement with chromatic depth splitting in the object beam path by a chromatic power according to at least one of claims 5 to 16, characterized in that the imaging system for the object with at least one grin lens ( 6b ) is trained. Spectral two-beam interferometer arrangement with Chromatic depth splitting in the object beam path through a Chromatic refractive power according to at least one of claims 5 to 17, characterized in that in the imaging system at least arranged a refractive element with chromatic transverse aberration by which the lateral chromatic aberration for the object sub-beam, the unwanted in the object beam path is present, at least approximately null is done. Spectral two-beam interferometer arrangement with Chromatic depth splitting in the object beam path through a Chromatic refractive power according to at least one of claims 5 to 17, characterized in that in the imaging system at least arranged a diffractive zone element with lateral chromatic aberration by which the lateral chromatic aberration for the object sub-beam, the unwanted in the object beam path is present, at least approximately made to zero. Spectral two-beam interferometer arrangement with chromatic depth splitting in the object beam path by a chromatic power according to at least one of claims 5 to 19, characterized in that in a Mirau interferometer, a hybrid element is arranged by means of two-sided substrate, in which on the imaging system associated substrate side partially transparent mirror layer is arranged, which serves as a beam splitter surface ( 9 ), said substrate side being concave ( 8b ) is formed, and on the other side of the substrate, a phase-zone structure ( 11a ) is applied with beam-focusing effect in the first diffraction order or that the substrate system associated with the substrate side convex ( 8a ) is formed, and on the other side of the substrate, a phase-zone structure is applied with beam divergent effect in the first diffraction order. Spectral two-beam interferometer arrangement with Chromatic depth splitting in the object beam path through a Chromatic refractive power according to at least one of claims 5 to 19, characterized in that the two-beam interferometer arrangement as Twyman Green, Michelson or Mach-Zehnder arrangement is formed.