DE102009017144A1 - Device and method for measuring a lens system, in particular an eye - Google Patents

Abstract

The invention relates to a device (1) for measuring a lens system, in particular the eye (2). The device (1) comprises an OCT measuring system (30) which comprises a light source (35) for emitting a first light bundle (32) of a first wavelength range, and at least one further optical measuring system (8, 9) comprising a light source (10 , 21) for emitting a second light beam (11, 22) of a second wavelength range (λ1, λ2). A diffractive optical element (18) is arranged in a common beam path region (14) of the measuring systems (30, 8, 9), which deflects the first and second light bundles (32, 11 or 32, 22) at least predominantly into different diffraction orders.

Description

The The invention relates to a device for measuring a Lens system, in particular one (human or animal) Eye. The invention relates in particular to a device for measuring the optical thickness and at least one other Property of the lens system, in particular the surface topography and the wave aberration.

For Surgery on the human eye such as the Correction of ametropia of the eye will be more recent Time increases the ablation of corneal tissue (LASIK procedure) by means of Excimer laser used. For this an upper layer (Flap) the cornea (cornea) cut open and folded to the side. Then the exposed corneal tissue becomes an appropriate amount ablated on tissue and then replated the corneal flap again. An accurate and comprehensive measurement of the different optical elements of the eye is on the one hand of crucial importance for the success of the treatment and on the other hand can also serve Exclusion criteria to consider that are against treatment speak one eye. In this sense, one is possible precise knowledge of the corneal thickness, the surface topography the cornea as well as the wave aberration of the eye required.

A similar Information density is also for other correction procedures in the human eye, in particular for a replacement of the Eye lens through an artificial implant (cataract surgery) and required for a corneal transplant.

So far are the corneal thickness, the topography of the cornea and the wave aberration of the eye is usually measured separately. This often results in discrepancies between the two due to measurements performed in chronological order the instability of the eye as a biological object on the one hand and on the other hand due to the numerous degrees of freedom of adjustment of the eye relative to the measuring device. When used in the Optical medicine can be such a measurement discrepancy in particular the Success of a surgical procedure on the eye or another medical correction procedure. to Avoiding such discrepancies is therefore a common measure Cornea thickness, topography and wave aberration desirable.

A device for the common measurement of the topography and wave aberration of the eye is out DE 103 42 175 A1 known. In this device, two optical measuring systems are provided with a common beam path area. A first measuring system which serves for topography measurement comprises a light source for emitting a first light beam of a first wavelength. The second measuring system, which is used to measure the wave aberration, comprises a light source for emitting a second light beam of a second wavelength. Here, a diffractive optical element is arranged in a common beam path region of the first measuring system and the second measuring system, which adjusts the respective wavefront profile of the first light beam and the second light beam wavelength-selective.

The Measuring the optical power of an eye, in particular the corneal strength (pachymetry) becomes particular today by means of so-called optical coherence spectroscopy (Optical Coherence Spectroscopy - OCT). The OCT measurement must be separated according to conventional technology performed by measuring other properties of the eye become.

Of the Invention is based on the object, a device for surveying a lens system, in particular an eye to indicate, the one simultaneous measurement of corneal strength and at least one further property of the lens system, in particular the (surface) topography and / or wave aberration. The term "simultaneous" is to understand that all measurements either at the same time and be carried out in parallel, or for a short time consecutively in a common measuring process, in particular oh ne to replace the meter or regarding the To have to dislocate to be measured lens system.

These The object is achieved by the features of claim 1. Thereafter, the device comprises a OCT measuring system with a light source to emit a first Light bundle of a first wavelength range includes, and at least one further optical measuring system with a Light source for the emission of a second light beam a second wavelength range. In a common Beam path range of both measuring systems is within the scope of the device a diffractive optical element (DOE) arranged, which is the first and second light bundles at least predominantly in different diffraction orders directs.

As is known, the use of the DOE advantageously makes it possible to "decouple" the OCT measurement beam, ie the first light beam from the second light bundle of the second measurement system, and thus enables the simultaneous use of both measurement systems without impairing the quality of the OCT measurement. In addition, it has been shown that a simple, yet effective beam guidance of the OCT measuring beam is possible by means of the DOE. In particular, by means of the DOE the Focus the OCT measuring beam onto the sample so that the reflected or scattered light is effectively recovered and directed back into the measuring system. This also ensures, among other things, that the incident light intensity on the sample can be kept low with sufficient recording quality.

preferred Embodiments and further developments of the invention are set forth in the dependent claims and arise from the description below.

Thus, the second measuring system is preferably set up for measuring the (surface) topography or for measuring the wave aberration. The (surface) topography is the three-dimensional shape of the lens surface. In the case of the eye, this lens surface is the surface of the cornea, ie the transparent cornea. The term wave aberration generally refers to the deviation of the optical imaging properties of the real lens system to be tested from the imaging properties of a corresponding ideal lens system. In the case of the eye, the wave aberration includes first order aberrations such as myopia, hyperopia or astigmatism as well as higher order aberrations. For carrying out the topography measurement or wave aberration measurement, the second measuring system is preferably in the manner of the respective in DE 103 42 175 A1 constructed measuring system.

Furthermore The device may be in addition to the OCT measuring system as well several other measuring systems included. In this case, according to the invention at least a light beam associated with another measuring system and the OCT measuring beam from the DOE preferably in different diffraction orders directed.

The Wavelength ranges of the first and second light bundles are preferably disjoint, ie spectrally overlap-free. Conveniently, there is the second light beam It consists of monochromatic light, ie light with essentially a discrete wavelength. The wavelengths the first and / or second light beam are preferably in the (non-visible) near-infrared region of the electromagnetic Spectrum.

In A first variant of the invention is the diffractive optical element formed such that it the first light beam, d. H. the OCT measuring beam, at least predominantly in the zeroth Diffraction order directs, and thus the beam path of the first light beam not, at least not significantly, changes. On the other hand the second light beam through the DOE at least predominantly directed in the first diffraction order. The second measuring system is in this process variant expediently designed to measure the topography. Preference is given here the zeroth diffraction order of the second light beam completely suppressed.

In A second variant of the invention is the diffractive optical element formed such that it the first light beam, d. H. the OCT measuring beam, at least predominantly in the first Diffraction order directs, whereas it passes through the second light beam the DOE at least predominantly in the zeroth diffraction order directs. The second measuring system is in this process variant expediently for Measurement of the wave aberration formed.

The diffractive optical element is in the second variant of the invention preferably designed such that it predominantly in the first diffraction order directed first light bundle in terms of his Wavefront course to the topography of the lens system. This pre-adjustment is made such that the wavefront progression of the first light bundle in the area of the cornea one of these has approximately corresponding curvature, so that the OCT measuring beam everywhere approximately perpendicular to the cornea surface impinges. These Pre-adaptation of the wavefront course to the corneal curvature ensures that the OCT measuring beam through essentially vertical reflection reflected particularly effective in the measuring system becomes. By pre-fitting the wavefront course is with others Words of light loss z. B. reduced by stray light. In application of the invention to the human eye as to be tested Lens system, the DOE is preferably designed such that the wavefront course of the first light beam to a standard medical model of the human eye, in particular Gullstrand's normal eye is preceded.

The DOE is preferably transparent, so that the first and second light bundles thrown through the DOE on the lens system. alternative But is also the use of a reflective DOE in the context of Invention conceivable.

Particularly suitable as a DOE is a surface-corrupted phase element. This is understood as a plate made of glass or a transparent plastic, in the surface of a relief-like diffraction grating is introduced. By means of computer-assisted production methods and suitable etching techniques, such a phase element can nowadays be manufactured comparatively inexpensively with extremely high precision. Here, the diffraction effect of the phase element can be highly flexibly adapted to the needs. With a surface-corrected phase element is in particular a surface grid with extremely small Gitterperio de on the order of a few hundred nanometers and thus a comparatively large deflection angle of the diffracted light achievable. In principle, however, it is conceivable that DOE in other ways, for. B. by a volume hologram or a reflective diffractive element to realize. In particular, it is also conceivable to carry out the DOE as a freely controllable, flexible optical element. This is possible for example by phase-shifting liquid crystal displays (LCD).

Around the refractive power and the orientation of an eye to be examined during the duration of the measurement, and thus the To increase measurement accuracy is preferably provided by another bundle of light a fixation target in the eye display. A fixation target is an image understood the subject to be examined during the measurement is offered for consideration. By the test person the fixation target Anvisiert, he automatically holds both the orientation of Eye as well as the eye's refractive power in a good approximation constant. The used for the insertion of the fixation target further light bundles has a further wavelength, for which preferably the DOE is also ineffective. The another wavelength is preferred both from the first wavelength as well as different from the second wavelength. To this Way is guaranteed that this further light beam the parallel measurements (pachymetry and topometry and / or wave aberration) unaffected. In a simplified version of the However, the device according to the invention is alternative provided that the wavelength of the for insertion of the Fixation targets used wavelengths of light one of the at least two measuring systems corresponds.

The Measurement of corneal strength by OCT, and or each further measurement of the wave aberration, topography, etc. are preferred at the same time carried out. A temporally sequential, d. H. one (in particular in a very short distance) staggered measurement is still considered with a view to simplified process implementation advantageous embodiment of the invention provided. This is especially true when using one for more than one Measuring system shared detector for better separation the measurement signals of these measuring systems makes sense. To avoid measurement discrepancies the measurements are preferably carried out at a time interval, which falls below the reaction time of the eye, so that the measurements with respect to the eye quasi-simultaneous.

following Be embodiments of the invention with reference to a Drawing explained in more detail. Show:

1 a schematic representation of an apparatus for measuring a human eye with a measuring system for measuring the topography, a measuring system for measuring the wave aberration and an OCT measuring system for measuring the corneal thickness and with a arranged in a common beam path range of the three measuring systems diffractive optical element ( DOE)

2 in a schematic representation of an OCT unit of the OCT measuring system according to 1 .

3 in an enlarged detail representation of a variant of the device according to 1 .

4 in illustration according to 3 a further variant of the device according to 1 with a modified beam path of the OCT measuring system,

5 in illustration according to 1 a second embodiment of the device,

6 in illustration according to 3 an enlarged detail of the device according to 5 , and

7 in illustration according to 1 a third embodiment of the device.

each other corresponding parts and sizes are in the figures always provided with the same reference numerals.

1 shows a schematic sketch of a device 1 for measuring corneal strength, corneal topography and wave aberration of a human eye 2 ,

The (surface) topography is the three-dimensional shape of the lens surface. In the case of the eye 2 This lens surface is the surface of the cornea 4 , ie the transparent cornea. The lens system of the eye 2 further includes in a known manner the eye lens 5 and the vitreous 6 , In which the eye lens 5 Opposite fundus is in a known manner the retina 7 (or retina) arranged.

The term wave aberration generally refers to the deviation of the optical imaging properties of the real lens system to be tested from the imaging properties of a corresponding ideal lens system. In the case of the eye 2 Wave aberration includes first order aberrations such as myopia, hyperopia or astigmatism, as well as higher order aberrations.

To measure the topography of the cornea 4 (Topometry) is the device 1 with a (topometry) measuring system 8th Mistake.

The measuring system 8th includes a light source 10 , in particular a laser. The light source 10 generates a light beam 11 a wavelength λ1. The light beam 11 is along the beam path of the measuring system 8th first in a collimator lens 12 parallel, via a bowling telescope 17 expanded, and by means of a wavelength-selective beam splitter 13 in a common beam path area 14 the measuring systems 8th and 9 irradiated. Within the beam path area 14 passes through the light beam 11 an eye 2 immediately upstream diffractive optical element, hereinafter abbreviated as DOE 18 designated. By the following in its operation described in detail DOE 18 becomes the light beam 11 in the direction of the eye 2 collimated. A share of the eye 2 incident light beam 11 (simplified in the following as a reflected light beam 11 ' designated), becomes on the surface 3 the cornea 4 reflected and opposite to the direction of incidence by the DOE 18 , the beam splitter 13 and the bowling telescope 17 thrown back. By one outside the common beam path area 14 arranged another beam splitter 19 becomes the reflected light beam 11 ' from the incoming light beam 11 decoupled and on a wavefront detector 20 directed. The bowling telescope 17 is designed in such a way that the cornea 4 on the wavefront detector 20 is shown sharply. The wavefront detector 20 is optionally designed as a Shack-Hartmann sensor, such as in US 2003/0038921 A1 is described. Alternatively, the wavefront detector 20 also be designed as an interferometer, in particular shearing interferometer.

For measuring the wave aberration (aberrometry) the device comprises 1 an (aberrometry) measuring system 9 , The measuring system 9 includes another light source 21 , The light source 21 , which in turn is preferably realized by a laser, emits a (relatively fine) light beam 22 a wavelength λ2. The light beam 22 is in a collimator lens 12 collimated and through another bowling telescope 17 and the wavelength-selective beam splitter 13 in the common beam path area 14 irradiated. Due to its wavelength selectivity, the beam splitter 13 for the wavelength λ2 transparent, thus ineffective. A beam splitter 13 with such wavelength selectivity can be produced by conventional technology, for example by a dielectric mirror.

In the further course of its beam path, the light beam falls 22 through the DOE 18 through to the eye 2 , The light beam 22 intervenes the DOE 18 virtually unmodified and continues to fall as a fine light beam through the cornea 4 and the eye lens 5 on the retina 7 , The light beam 22 becomes at the retina 7 diffused back scattered. This scattered light, hereinafter as backscattered light beam 22 ' referred, falls through the eye lens 5 , the cornea 4 , the DOE 18 , the Kepler telescope 17 and the beam splitter transparent to the wavelength λ2 13 back against his direction of incidence. By one outside the common beam path area 14 in the beam path of the light beam 22 . 22 ' positioned another beam splitter 23 becomes the backscattered light beam 22 ' decoupled and on a wavefront detector 24 of the measuring system 9 thrown. The wavefront detector 24 is in turn optionally designed as a Shack-Hartmann sensor or as an interferometer. The beam splitters 13 and 23 is optional a pre-compensation unit 25 interposed. This pre-compensation unit 25 contains a (not shown in detail) conventional optical zoom system or a lens arrangement, with which the defocus and astigmatism components, ie, the short- or hyperopia and the astigmatism, can be compensated. The pre-compensation unit 25 It also reverses the incoming light beam 22 sharp on the retina 7 map.

This in 1 represented DOE 18 is a so-called surface-corrupted phase element, its structure and functioning in connection with the measuring systems 8th and 9 in DE 103 42 175 A1 is described in more detail.

The device 1 also includes another light source 26 through which another light beam 27 a wavelength λ3 to the eye 2 is displayed. The third light bundle 27 will turn through a collimator lens 28 collimated and by means of a wavelength-selective beam splitter 29 on the eye 2 aligned. The third light bundle 27 serves to the eye 2 to offer a so-called fixation target. This is understood to mean a picture which the test person aims at during the measurement. By sighting the fixation target becomes the visual axis of the eye 2 along the optical axis of the common beam path area 14 aligned. The other is the refractive power of the eye lens 5 fixed in a region in which the subject can recognize the fixation target sharply. In particular, the subject is often faked by the fixation target an image at infinity, so that the eye lens 5 is kept in the relaxed state during the measurement. The light beam 27 also passes through the - possibly existing - pre-compensation unit 25 in particular, a possible myopia of the eye 2 To compensate, and thus the subject at all the opportunity to target the fixation target sharply.

For the measurement of corneal strength (pachymetry) the device comprises 1 an OCT messsys tem 30 , The OCT measuring system 30 comprises an OCT unit (described in more detail below) 31 , which is a ray of light 32 generated in the form of a fine measuring beam. The light beam 32 has a continuous spectral distribution within a spectral band of typically between 30 nm and 100 nm about a central wavelength λ4.

The light beam 32 is via another collimator lens 33 and another beam splitter 34 in the common beam path area 14 introduced and occurs coaxially or parallel offset to the optical axis of the common beam path range 14 through the beam splitter 13 and the DOE 18 therethrough. The light beam 32 is intended to be centrally on the cornea 4 , where the light beam 32 Partially reflected on the cornea outer surface and on the cornea inner surface. The reflected light beam 32 is over the beam splitter 34 and the collimator lens 33 into the OCT unit 31 returned and detected there.

The beam splitter 13 is with respect to the spectral distribution of the light beam 32 formed such that the light beam 32 respectively. 32 ' the beam splitter 13 happened unhindered.

At the OCT unit 31 is it according to 2 preferably a designed like a Michelson interferometer frequency domain OCT measuring device. The OCT unit 31 then includes a light source 35 , in particular in the form of a so-called superluminescent diode. The light emitted by this light is transmitted via a beam splitter 36 in the light beam 32 and a reference beam 37 divided up. The reference beam 37 gets at a mirror 38 reflected, wherein the reflected reference beam 37 ' back to the beam splitter 36 is thrown. Through the beam splitter 36 becomes the reflected reference beam 37 ' with the reflected light beam 32 ' superimposed and together with the latter on a detector 39 thrown in the form of a spectrometer. Based on the spectral distribution of the superimposed and interfering light bundles 32 ' and 37 ' the corneal thickness is calculated in a conventional manner.

Alternatively to the in 2 represented OCT unit 31 Other conventional OCT measuring arrangements can also be used within the scope of the device 1 are used, in particular so-called time domain measuring arrangements.

The wavelength λ1 of the light beam 11 is preferably set to 1064 nm. The light beam 11 is thus in the (non-visible) infrared range of the electromagnetic spectrum, so that the topometry measurement of the eye 2 is not perceptible. The DOE 18 is - in adaptation to the wavelength λ1 - designed such that the light beam 11 completely deflected into the first diffraction order while the DOE 18 the zeroth diffraction order of the light beam 11 completely, or at least almost completely suppressed (see also DE 103 42 175 A1 ).

The DOE 18 is further configured such that the diffracted light beam 11 in the area of the cornea 4 has a curved wavefront course corresponding to the average surface curvature of the human cornea. This average value is derived in particular from the standard eye model by Gullstrand.

The wavelength λ2 of the light beam 22 . 22 ' is optimally set to 532 nm in optical terms. In this case, the light beam 22 . 22 ' through the DOE 18 transmitted exclusively in the zeroth order of diffraction. The light beam 22 goes through the DOE 18 So with at least almost unchanged wavefront course. To the visual perceptibility of the light beam 22 Alternatively, the wavelength λ2 is alternatively set to wavelengths in the range between 690 and 750 nm, and thus to the transition between the red and the infrared spectral range. In the latter case, the light beam 22 Although not complete, but mostly in the zeroth diffraction order of the DOE 18 transmitted.

The wavelength λ3 of the light beam 27 must necessarily be in the visible spectral range and is preferably selected such that the DOE 18 no diffractive effect on the light beam 27 exercises. The wavelength λ3 is preferably set to 635 nm (red). To simplify the measurement setup, however, the wavelength λ3 can also be selected to be equal to the wavelength λ2. In this case, the light beam 27 during the aberration measurement temporarily faded out. Alternatively, however, the wavelength λ3 may also be selected such that the DOE 18 the zeroth diffraction order of the light beam 27 suppressed.

The central wavelength λ4 of the light beam 32 . 32 ' is in the embodiment according to 1 chosen so that the DOE 18 the light beam 32 at least predominantly transmitted in the zeroth diffraction order, that is essentially unchanged pass. For this purpose, the central wavelength λ4 is determined in particular on the outer edge of the red spectral range, in particular to a value between 500 nm and 750 nm, in particular 532 nm.

In the embodiment of the OCT measuring system 30 according to 1 is the beam path of the light beam 32 in terms of its position relative to the optical axis of the common beam area 14 fix. The light beam 32 is thus always in the same place of the cornea 4 , in particular directed to its center.

In variants of the device 1 according to 3 and 4 is the beam path of the light beam 32 on the other hand changeable by means of a deflection device, not shown here, so that the surface of the cornea 4 by shifting the light beam 32 can be scanned. That's the light beam 32 according to 3 opposite the optical axis of the common beam area 14 movable in parallel. According to 4 is the light beam 32 alternatively, with respect to the optical axis of the common beam area 14 pivotable, in such a way that the light beam 32 everywhere approximately perpendicular to the cornea surface.

Incidentally, the same design variants of the device 1 according to 3 and 4 the in 1 illustrated embodiment. In particular, the light beam is 32 through the DOE 18 always predominantly transmitted in the zeroth diffraction order, and thus enforces the DOE 18 essentially without change of direction.

In the 5 illustrated second embodiment of the device 1 differs from the embodiments described above mainly in that here the light beam 32 , That is, the OCT measuring beam, is generated in a spectral range in which the light beam 32 through the DOE 18 predominantly transmitted in the first diffraction order. That within the common beam path area 14 parallel to the optical axis extending light beam 32 becomes thereby after passing through the DOE 18 deflected towards the optical axis and onto the cornea 4 collimated. As a result of the described embodiment of the DOE 18 (Pre-adjustment of the first-order diffracted wavefront profile to the average corneal curvature) becomes the light beam 32 in this case deflected so that it is always approximately perpendicular to the surface of the cornea 4 impinges (see also 6 ).

The central wavelength λ4 of the light beam 32 For this purpose, it is preferably fixed to one of the wavelengths λ1 equal or similar amount.

To by means of the light beam 32 the surface of the cornea 4 to be able to scan has the OCT measuring system 30 according to 5 a beam deflector 40 (also: angle scanner), with the light beam 32 by a variable solid angle from its original propagation direction transverse to the optical axis of the common beam region 14 is distractible. Through one of the beam deflector 40 downstream collimator lens 41 becomes the light beam 32 again transversely to the optical axis of the common beam area 14 aligned.

In the 7 illustrated third embodiment of the device 1 is essentially related to 5 and 6 described embodiment. In contrast to this is according to 7 but the light beam 32 first in the beam path of the topometry measuring system 8th appears. The beam splitter 34 is within the Kepler telescope 17 of the measuring system 8th arranged. The light beam 32 then here together with the light bundle 11 through the beam splitter 13 parallel to the optical axis of the common beam path area 14 aligned.

To the beam path of the light bundles 11 . 11 ' and 32 . 32 ' in the embodiments of the device 1 according to 5 and 7 to be able to separate, the wavelengths λ1 and λ4 are preferably selected with a small spectral distance from each other. Preferably, the wavelength λ1 to 1064 nm, and the wavelength λ4 set to 930 nm. The beam splitters 13 (in the embodiment according to 5 ) respectively. 34 (in the embodiment according to 7 ) are in this case correspondingly narrow-band design to a clean separation of the light beam 11 . 11 ' and 32 respectively. 32 ' to ensure.

Alternatively, the light beams 11 . 11 ' and 32 . 32 ' in the embodiment according to 7 also be set to the same wavelength length amount, in particular to 1064 nm. In this case, the beam splitter 34 suspended in such a way that it can be used for pachymetry measurement in the beam path of the measuring system 8th pivoted in, and for the topometry measurement from the beam path of the measuring system 8th can be swung out. The pachymetry measurement and the topometry measurement must be performed alternately with each other over time.

All the above-described embodiments and variants of the device 1 is common that one of the light bundles 11 . 11 ' or 22 . 22 ' preferably in a different diffraction order of the DOE 18 is transmitted as the light beam 32 . 32 ' , In this way, it is ensured that at least one of the further measurements can be carried out simultaneously with the pachymetry measurement.

1

contraption

2

eye

4

cornea

5

eye lens

6

vitreous

7

retina

8th

(Topometry) measuring system

9

(Wellenaberrations-) measuring system

10

light source

11 11 '

light beam

12

collimator lens

13

beamsplitter

14

(Common) Beam path area

17

Kegler telescope

18

diffractive optical element (DOE)

19

beamsplitter

20

Wavefront detector

21

light source

22 22 '

light beam

23

beamsplitter

24

Wavefront detector

25

precompensation

26

light source

27

light beam

28

collimator lens

29

beamsplitter

30

OCT measuring system

31

OCT unit

32 32 '

light beam

33

collimator lens

34

beamsplitter

35

light source

36

beamsplitter

37, 37 '

reference beam

38

mirror

39

detector

40

Beam deflector

41

collimator lens

λ1

wavelength

λ2

wavelength

λ3

wavelength

λ4

Central wavelength

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 10342175 A1 [0005, 0011, 0037, 0044]
• US 2003/0038921 A1 [0034]

Claims (6)

Contraption ( 1 ) for measuring a lens system, in particular of the eye ( 2 ), - with an OCT measuring system ( 30 ), which is a light source ( 35 ) for the emission of a first light bundle ( 32 ) of a first wavelength range, and - with at least one further optical measuring system ( 8th . 9 ), which is a light source ( 10 . 21 ) for the emission of a second light bundle ( 11 . 22 ) of a second wavelength range (λ1, λ2), - wherein in a common beam path range ( 14 ) of the measuring systems ( 30 . 8th . 9 ) a diffractive optical element ( 18 ) is arranged, which the first and second light beam ( 32 . 11 respectively. 32 . 22 ) at least predominantly in different diffraction orders directs. Contraption ( 1 ) according to claim 1, wherein the second measuring system ( 8th . 9 ) is set up to measure the topography or to measure the wave aberration. Contraption ( 1 ) according to claim 1 or 2, wherein the diffractive optical element ( 18 ) the first light bundle ( 32 ) at least predominantly in the zeroth diffraction order, and the second light bundle ( 11 ) directs at least predominantly in the first diffraction order. Contraption ( 1 ) according to claim 1 or 2, wherein the diffractive optical element ( 18 ) the first light bundle ( 32 ) at least predominantly in the first diffraction order, and the second light bundle ( 22 ) at least predominantly in the zeroth diffraction order directs. Contraption ( 1 ) according to claim 4, wherein the diffractive optical element ( 18 ) is formed such that it the first light beam ( 32 ) with respect to its wavefront profile to the topography of the lens system ( 2 ). Contraption ( 1 ) according to one of claims 1 to 5, wherein the diffractive optical element ( 18 ) is designed as a surface-corrupted phase element.