DE102020201808A1 - Method and device for aligning an optical element in a beam path - Google Patents

Abstract

The invention relates to a method and a device for aligning at least one element, in which radiation is guided along a beam path (2) and detected by means of a detector (7) which has a plurality of detector elements (7.n). that for the purpose of aligning the at least one element, a phase element (4) connected to the element to be aligned is introduced into the beam path; the radiation is divided into at least two partial beams (5.1 to 5.4) by means of the phase element (4) and each of the partial beams (5.1 to 5.4) is directed onto mutually different detector elements (7.n) of the detector (7) and at least one parameter of the partial beams ( 5.1 to 5.4) is recorded. The parameters of the recorded partial beams (5.1 to 5.4) are recorded as actual values and compared with a target value. Based on the comparison of the actual and target values, current position parameters of the (optical) element of the beam path (2) are determined and control commands are generated by means of which the current position parameters of the (optical) element are used to align the actual values with the target values being affected.

Description

The invention relates to a method and a device for aligning an element in a beam path, in particular in a detection beam path of a microscope.

A fundamental problem in optical instruments relates to the alignment of, in particular optical, elements and components with respect to other elements or with respect to an optical beam path of an optical arrangement. Depending on the position in the beam path, an alignment of optical elements relative to one another can be observed directly or by means of aids that can be introduced. For example, autocollimation telescopes (AKF; autocollimators) can be used, which are attached to the optical input or output of an optical instrument and enable the components to be aligned under direct observation. However, components are not always freely accessible and observable and, due to their compact designs, there is often no possibility of attaching optical aids for adjustment in the instrument or at the instrument outputs.

On the other hand, optical instruments often contain light detectors, which must also be aligned to the beam path, so are part of the optical path or beam path and which must often not be removed in order to z. B. to be temporarily replaced by an AKF.

Modern laser scanning microscopes (LSM) such as the LSMs 800/900 and LSMs 880/980 (Carl Zeiss Microscopy GmbH) have detectors with 32 channels (= 32 detector elements) that enable fast confocal parallel scanning of the so-called point spread function (PSF) of the microscope during the microscopic image scanning. Such detectors are also referred to below as Airyscan detectors. The Airyscan detector is arranged as a detector plane in an image plane conjugated to the point of origin of the detection radiation or to the focus. The detection radiation impinging on the detector, including extra-focal components, is recorded with the large number of detector elements, which enables the recording and evaluation of the respective local distribution of the intensities of the detected detection radiation ( Huff, J. 2015: The Airyscan detector from ZEISS: confocal imaging with improved signal-to-noise ratio and super-resolution; Nature Methods 12, i-ii; https://doi.org/10.1038/nmeth.f.388 ).

One possibility known from the prior art for aligning a light beam with respect to a detector consists in directing the light beam onto a detector which has a plurality of detector elements or detector surfaces. If, for example, the same measured values, for example the intensity, are recorded from all detector elements acted upon by the light beam, a symmetrical alignment of the light beam with respect to the axis of the detector (detector axis) can be concluded. Correspondingly, different measured values of the detector elements can be evaluated and used in order to generate control commands and, for example, to align the light beam and the detector with one another by means of driven actuating means. With such a procedure, however, slight angular errors in the alignment of optical elements with respect to one another cannot be recognized, or only inadequately.

The invention is based on the object of proposing a possibility for aligning, in particular, optical elements of a beam path, in which angle errors can also be recognized.

The object is achieved by the subjects of the independent claims. Advantageous refinements can be found in the dependent claims.

The object is achieved with a method for aligning at least one element in which radiation is guided along the beam path and detected by means of a detector which has a plurality of detector elements. The element to be aligned is in particular an optical element such as a lens, a diaphragm, a filter, a mirror or the like. Even if an element or a component that is not optically effective can in principle also be aligned by means of the invention, the invention is to be explained below with reference to an optical element. The beam path is in particular a detection beam path in which radiation (light beam) is guided and detected by means of the detector.

The method is characterized in that, for the purpose of aligning the at least one (optical) element, a phase-changing / phase-shifting element connected to the element to be aligned (hereinafter for short: phase element) is introduced into the beam path. The radiation (also: beam), more precisely: the beam, is divided into at least two partial beams by means of the phase element. Each of the partial beams is directed onto different detector elements of the detector, which are spatially separated from one another and are adjacent to one another, for example, in a detection plane lying orthogonally to the detector axis. The detector elements detect at least one parameter of the partial beams as measured values, for example the intensity values of the respective partial beams. The so The actual values obtained are compared with corresponding setpoint values which, for example, are set individually for the individual partial beams. Current position parameters of the optical element are determined on the basis of the comparison of the actual and target values. In addition to the coordinates of the optical element, these can also be its relative angular position. The determined coordinates and / or angular positions form the basis for generating control commands, the execution of which influences current position parameters of the optical element for aligning the actual values with the target values.

The detector, which is already arranged in the beam path, can advantageously be used to carry out the method according to the invention, as a result of which a costly exchange of the detector for an adjustment aid can be avoided. If the optical element is not aligned, the detector can therefore be used to detect detection radiation.

The phase element is preferably connected directly to the optical element to be aligned and, for example, fastened on or to it. Alternatively, the phase element can also be connected to the optical element indirectly, for example via a mechanical gear or a joint. It is only important that current position parameters of the optical element are related in a one-to-one manner to the current position and the respective optical effects of the phase element.

The principle of the invention is exemplified in 1a and 1b shown. Along a beam path 2 If a beam (light beam) of radiation, in particular light in the visible and / or infrared wavelength range, propagates in parallel and strikes an optical element to be adjusted 3 and then on to a phase element 4th . The phase element 4th is with the optical element to be adjusted 3 for example mechanically connected. The phase element 4th is designed here as a phase mask. In further versions, the phase element 4th for example in the form of a grid. By the action of the phase element 4th the radiation is divided into, for example, two partial beams 5.1 and 5.2 and by means of a downstream optical system 6th on different detector elements 7, 7.2 , 7.3 , 7.4, ... to 7.n of a detector 7th steered. The measured values of the respective partial beams 5.1 and 5.2 are recorded by means of a correspondingly configured control unit 10 compared to each other. In the in 1a the situation shown is the element to be adjusted 3 not in the middle of the beam path 2 the radiation hits the phase element offset 4th . The partial beams 5.1 and 5.2 cause different measured values. For example, the first partial beam 5.1 results in a proportion of 70% and the partial beam 5.2 a proportion of 30% of the total in a detection plane 8th detected intensity transported. To those on the illuminated detector elements 7.1 to 7.n The phase element must adjust the irradiated intensities to one another 4th for example, be shifted in the direction of the higher intensity. Are the geometry of the beam and the design of the phase element 4th as well as their resulting optical effect are known, the relative intensities can be used to determine the distance by which and in which direction the phase element 4th must be moved to match the intensities. Shifting takes place either manually or by executing in the evaluation and control unit 10 generated control commands by means of a drive unit 11 . The directions and distances of the movement of the phase element required for a correction 4th can be on an ad 19th can be displayed to allow manual correction, for example.

For example, if the in 1a If the situation shown is recognized, control commands can be generated on the basis of the recorded measured values, in this case on the basis of the recorded intensities, the execution of which results in a change in the position of the radiation. The change in position is brought about in such a way that uniform illumination of the phase element 4th takes place, which is reflected in the same intensities of 50% each of the partial beams 5.1 and 5.2 ( 1b) .

In the 1b is a centered on the phase element 4th incident beam of radiation shown. This is divided into partial beams 5.1, 5.2 of the same intensity and in the detection plane 8th by means of the detector elements 7.1 to 7.n recorded.

In the 1a and 1b it can be seen that the area of the phase element 4th should be larger than the cross-section of the beam. If the phase element 4th is smaller than the beam cross-section, would with almost every positioning of the phase element 4th 50% of the radiation in each of the two spots 9 (please refer 4th ) to get distracted. Only if there is a strong shift in the phase element 4th If this is partially moved out of the beam path, a proportionally different division of the intensities would occur. A sensitive adjustment of optical elements 3 each other would hardly or not be possible at all.

For example, if the beam diameter is 4.2 mm, then the phase mask could 4th z. B. 5 mm in diameter (schematically in 2 shown). With an exemplary beam diameter of 4.2 mm, a shift of 42 µm (1%) results in a change in the intensities in the spots 9 of 2% each (the assumed edge length the quadrant along the diameter is 2.1 mm, therefore 42 µm corresponds to 2%). The relative change in the intensities of both spots 9 to each other is around 4%. A detection accuracy of, for example, 40 μm can therefore be achieved by means of the solution according to the invention.

The basic idea of the invention therefore consists in deflecting portions of the incident bundle of parallel rays into different angles and thus onto different locations (spots) of the detector, in particular of an area detector. On the basis of the evaluation of the intensities detected at the different locations, that is to say by means of one or more detector elements, it can be determined when the deflecting element, in particular the phase element, is centered in the beam of radiation.

For example, a CCD array, an EMCCD, a CMOS, an sCMOS array or an array of photon avalanche diodes (APD) or single photon avalanche diodes (SPAD), an array of secondary electron multipliers (photon multiplying tube, PMT), a quadrant PMT detector, a quadrant photodiode or a 5-channel detector can be used. Measured values from a fixed or dynamically selected number of detector elements can be combined in the evaluation (so-called “binning”). A so-called Airyscan detector is advantageously used, in which a plurality of detector elements are arranged two-dimensionally.

The described principle of the invention can be expanded to two dimensions in further refinements. A phase mask (also: adjustment phase mask) can be divided into four quadrants, for example, which deflect the light in different spatial directions. This results in four separate partial beams which, through optical focusing, result in four points of light lying in a detection plane, the differences in intensity of which correspond to the offset of the phase mask in the beam path. In the simplest design of the phase mask, the quadrants are surfaces that are tilted towards one another and thus generate lateral beam deflections. More complex refractive and diffractive designs are discussed below.

The object is also achieved with a device which has at least one, in particular optical, element in a beam path. In this case, radiation is guided along the beam path, which is in particular a detection beam path, and detected by means of a detector. The detector has a plurality of detector elements.

A characteristic of a device according to the invention is that, for the purpose of aligning the at least one (optical) element, a phase element connected to the element to be aligned can be introduced into the beam path, in particular pivoted or pushed in.

The action of the phase element divides the radiation into at least two partial beams. Each of the partial beams is directed to mutually different detector elements of the detector, of which at least one parameter of the partial beams is or can be detected. Furthermore, there is an evaluation and control unit which is configured in such a way that parameters of the recorded partial beams are recorded as actual values and compared with setpoint values. Current position parameters of the optical element of the detection beam path are determined on the basis of the comparison of the actual and target values with one another. The configuration of the control unit allows the generation of control commands, by means of which the current position parameter of the element for aligning the actual parameters with the target parameters is or can be influenced.

The phase element can be present, for example, on or on a component in the form of a wheel, a cam disk or a slide. Such a component is, for example, a revolver, a filter wheel, a change wheel, a slide or a cam that can be swiveled into the beam path.

In different versions of the device, the phase element can be designed as a diffractive and / or a refractive element. The phase element can be, for example, a phase grating or a phase mask.

In a possible further embodiment of the device, the phase element is controllable and can be changed in a manually or automatically controlled manner. For example, the phase element is formed by an acousto-optical filter (AOTF) or an acousto-optical modulator (AOM).

The optical element to be aligned can optionally be introduced into and removed from the detection beam path in variably configured devices in order to enable different operating states and / or to allow better accessibility to the beam path.

It is advantageous if the detector remains in the beam path of the device and is set up to detect detection radiation. In this way, the detector can be used for data acquisition, for example for image acquisition, when the optical element is not being aligned. An exchange of the detector for example against an autocollimation telescope (AKF) for the purpose of alignment can advantageously be omitted.

In order to achieve the desired subdivision of the incident beam into partial beams and their deflection to different locations on the detector, the phase element has at least one structured area, the optical effect of which divides an incident beam of radiation into at least two, in particular four, partial beams. The partial beams do not overlap. The partial beams can be focused to light points (spots) in the detector plane by means of optical elements. Their differences in intensity correspond to the offset of the phase element in the beam path.

In one embodiment, the phase element, which is designed in particular as a phase mask, has a carrier layer which has the at least one structured region and at least one reference mark which is used for mounting the phase mask in the correct position. The reference mark can, for example, be a recess in the carrier layer. The carrier layer is, for example, a glass plate, in the surface of which the structured area is produced. This can be done, for example, by etching, grinding and / or coating.

For example, the phase element can be attached to the change wheel at a precisely defined location. The reference marks present on the phase element for the precise alignment of the phase element on the change wheel can be aligned and glued with respect to precise bores in the light passage openings of the change wheel. By introducing the phase element into the beam path and using the area detector, the change wheel can be correctly positioned in relation to the beam path.

The advantages of the method according to the invention, of the device and of the phase element, in particular the adjustment phase mask, result, for example, in the alignment of optical elements which were applied with precision to a change wheel. With the change wheel, the different elements could be swiveled into the beam path. Using the invention described, the change wheel could be aligned with the optical beam path. The invention allows the change gear, for example, to be aligned without, for example, a technician having to be equipped with an expensive AKF. If a PMT area detector, for example an Airyscan detector, is already present in the beam path and this is not to be removed first to simplify the adjustment process, the existing detector can be used for the alignment. Adjustment using the AKF, on the other hand, would require the detector to be removed.

The use of an adjustment phase mask, which generates four points of light with light transmission, for example, is a well-suited option for aligning instrumental assemblies with respect to an optical beam path (e.g. adjustment light beam) in an instrument with respect to other assemblies. The invention can generally be used in device construction.

The function of the phase elements does not necessarily have to be generated by purely static optical assemblies, but can also be implemented through the use of dynamic electro-optical or magneto-optical effects or processes. It is possible to use digitally controllable, i.e. time-varying phase masks such as B. spatial light modulators (SLM) or similar technologies.

The invention is advantageous for instruments with assemblies that are difficult to access and / or area detectors additionally present in the beam path (e.g. camera; with minimalist equipment a 2-pixel detector for an adjustment in one spatial dimension or a 4-pixel detector for an adjustment in two spatial dimensions).

• 1a eine schematische Darstellung des Vorgangs des Ausrichtens eines Phasenelements in einem Strahlengang mit unterschiedlichen Intensitäten der erzeugten Teilstrahlen;
• 1b eine schematische Darstellung des Vorgangs des Ausrichtens eines Phasenelements in einem Strahlengang mit gleichen Intensitäten der erzeugten Teilstrahlen nach Korrektur;
• 2 eine schematische Darstellung eines ersten Ausführungsbeispiels eines Phasenelements mit vier Quadranten;
• 3 eine schematische Darstellung eines Flächendetektors mit einer Mehrzahl von Detektorelementen sowie eine beispielhafte Anordnung von vier durch Teilstrahlen beleuchtete Bereiche (Spots);
• 4 eine schematische Darstellung eines Ausführungsbeispiels einer erfindungsgemäßen Vorrichtung;
• 5 eine schematische Darstellung einer Quadrantenphasenmaske mit zusätzlichen Justierelementen und einem Ausschnitt eines Bauteils;
• 6 eine schematische Darstellung eines zweiten Ausführungsbeispiels eines Bauteils mit einem Phasenelement;
• 7 eine schematische Darstellung eines vierten Ausführungsbeispiels eines Phasenelements in Form einer refraktiven Phasenmaske;

The invention is described in more detail below on the basis of exemplary embodiments and illustrations. Show it:

• 1a a schematic representation of the process of aligning a phase element in a beam path with different intensities of the partial beams generated;
• 1b a schematic representation of the process of aligning a phase element in a beam path with the same intensities of the partial beams generated after correction;
• 2 a schematic representation of a first embodiment of a phase element with four quadrants;
• 3 a schematic representation of an area detector with a plurality of detector elements and an exemplary arrangement of four areas illuminated by partial beams (spots);
• 4th a schematic representation of an embodiment of a device according to the invention;
• 5 a schematic representation of a quadrant phase mask with additional adjustment elements and a section of a component;
• 6th a schematic representation of a second embodiment of a component with a phase element;
• 7th a schematic representation of a fourth embodiment of a phase element in the form of a refractive phase mask;

The invention is explained on the basis of exemplary embodiments, the same reference symbols denoting the same technical units or elements, unless expressly stated otherwise.

In the already explained above 1a and 1b the principle of the invention is shown.

The phase element 4th can be divided into several partial areas 4th until 4.4 be subdivided ( 2 ). For example, the phase element, for example a phase mask, can be divided into four quadrants of equal size, each of which deflects the light away from the center of the phase element, as shown in FIG 2 is symbolized by arrows. The arrows represent the partial beams schematically 5.1 to 5.4 represent.

3 shows schematically an area detector in the form of a so-called Airyscan detector with a plurality of detector elements 7.1 to 7.n (for the sake of clarity denoted by 1 to 32) and an exemplary arrangement of four by partial beams 5.1 to 5.4 (not shown) illuminated areas 9 (Spots 9 ).

The four spots 9 should be detected on the area detector (e.g. camera; here: Airyscan detector). Several detector elements can be used for this purpose 7th .n are connected to each other (binning). That is to say, the recorded measured values of the relevant detector elements 7th .n are summarized and evaluated together. The so-called binning can be done using suitable software. In the exemplary embodiment shown, the detector elements are in each case 7th , 7.17 , 7.18 and 7.30 ; 7.2 , 7.8 , 7.9 and 7.21 ; 7.3 , 7.11 , 7.12 and 7.24 as 7.5 , 7.14 , 7.15 and 7.27 connected to each other (binned).

A first embodiment of a device according to the invention 1 is in 4th shown simplified. From a light source 12th radiation, in particular laser light, is provided and via a light-conducting fiber 13th in the beam path 2 coupled. The one from the end of the fiber 13th diverging radiation is generated by means of optics 6th collimated and by means of another optic 6th on the detector 7th in the detector plane 8th focused (solid line). For the purpose of adjustment, the phase element is 4th in the beam path 2 , brought in.

As a result of the optical effect of the phase element 4th becomes that on the phase element 4th incident bundle of rays in four partial rays 5.1 to 5.4 (only sections of two partial beams with broken solid lines are shown as an example), as is the case in principle for two partial beams in FIG 1a and 1b is shown. In the detector plane 8th become the four partial beams 5.1 to 5.4 in four spots 9 shown (see picture insert), measured values of the respective partial beams 5.1 to 5.4 and this to the evaluation and control unit 10 directed. In the evaluation and control unit 10 the recorded actual values of the measured values are compared with target values. If necessary, necessary corrections are derived from the result of the comparisons and the control commands required to carry out the corrections are generated. With the control commands, the drive unit 11 controlled and the alignment and position of the component 14th with the phase element 4th relative to the beam path 2 changes. The correction values determined can additionally or alternatively be shown on a display 19th , for example on a monitor, for example to manually correct the component 14th to enable.

In one possible embodiment of the device 1 is a phase element 4th in the form of a phase mask with a diameter of 5 mm, which is used on a beam path 2 was adjusted with a diameter of 4.2 mm. The phase element 4th generated in the focus of an optic 6th four spots with a focal length f2 of 100 mm 9 . Every spot 9 has a diameter of approx. 30 µm. The spots 9 are in the detector plane 8th about 100 µm apart. Becomes the phase element 4th for example by a distance of 50 µm laterally to the optical axis 3 shifted, this results in a change in the intensity of a spot 9 in the detector plane 8th in the amount of 3.5%. This corresponds to a relative change in intensity of 7% between two spots 9 . This is an alignment of the phase element 4th with an accuracy of 30 to 50 µm possible without any problems.

The phase element 4th is usually on a carrier layer 15th , for example on a glass plate, formed by, for example, in the carrier layer 15th a structured area 16 is etched. Around the mostly round phase element 4th as easily and precisely as possible on a component 14th such as aligning a carrier wheel, reference marks can be used 17th on the component 14th and / or on the carrier layer 15th be available for the correct mounting of the phase element 4th also known as the adjustment phase mask. This in 5 phase element shown 4th points to the backing layer 15th a structured area 16 and two adjustment elements as reference marks 17th on. Together with high-precision holes 18th in the component 14th can the phase element 4th , in this case a quadrant phase mask, very precisely aligned in place and angle and on the component 14th appropriate be by the structured area 16 and the reference marks 17th the carrier layer 15th with corresponding holes 18th of the component 14th be brought under cover.

One component 14th in the form of a wheel with precision bores and an applied phase element 4th is in 6th shown. The phase element 4th has four structured areas 16 on.

In practice, the tolerance requirement for the angular alignment of the quadrant phase mask is usually relatively low, whereas higher requirements are placed on the lateral positioning. The lateral positioning is carried out by positioning mechanics and electronics, e.g. B. electric stepper motors, piezo elements, precise positioning screws, optically equipped wheel mounts, linear slides or guides, etc., achieved in the interaction of the reproducibility of their approach accuracy and their manufacturing and accuracy tolerances. In practice, this is possible with moderate effort, i.e. relatively inexpensive mechanical and electrical components.

To a phase element 4th To generate a quadrant phase mask, for example, plane-parallel plates can be tilted and the resulting refractive effect of the plates can be used. Alternatively, four prisms can be used to generate the partial beams 5.1 to 5.4 to be available. Alternatively, a refractive design can be used, for which in 7th a schematic example is given. The continuous profile has a depth excursion of 3.6 µm and, when used in the in 4th The case shown is an illustration of four spots already described above 9 in the detector plane 8th . Compared to a diffractive design (see below), the etching depths are about 4 times greater, which means longer production times and an increased susceptibility to errors.

List of reference symbols

1

contraption

2

Beam path

3

(optical) element

4th

Phase element

4.1 to 4.n

Partial areas of the phase element 4

5.1 to 5.n

Partial beam

6th

optics

7th

detector

7.1 to 7.n

Detector element

8th

Detector level

9

Spot

10

Evaluation and control unit

11

Drive unit

12th

Light source

13th

fiber

14th

Component

15th

Carrier layer

16

structured area

17th

Reference mark

18th

Hole / breakthrough / recess

19th

advertisement

oA

optical axis

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Non-patent literature cited

• Huff, J. 2015: The Airyscan detector from ZEISS: confocal imaging with improved signal-to-noise ratio and super-resolution; Nature Methods 12, i-ii; https://doi.org/10.1038/nmeth.f.388 [0004]

Claims (13)

Method for aligning at least one element (3), in which radiation is guided along a beam path (2) and detected by means of a detector (7) which has a plurality of detector elements (7.n), characterized in that - for the purpose the alignment of the at least one element (3), a phase element (4) connected to the element to be aligned is introduced into the beam path, - the radiation is divided into at least two partial beams (5.1 to 5.4) by means of the phase element (4) and each of the partial beams (5.1 to 5.4) is directed onto mutually different detector elements (7.n) of the detector (7) and at least one parameter of the partial beams (5.1 to 5.4) is detected; - The at least one recorded parameter of the recorded partial beams (5.1 to 5.4) is recorded as an actual value and compared with a target value or compared; - Current position parameters of the element (3) of the beam path (2) are determined on the basis of the comparison of the actual and target values with one another; and - control commands are generated by means of which the current position parameter of the element (3) is influenced to align the actual values with the target values and / or necessary alignments of the actual values with the target values on a display (19) for an optional manual adjustment can be displayed. Procedure according to Claim 1 , characterized in that the detector (7) is used to detect detection radiation when the element (3) is not being aligned. Procedure according to Claim 1 or 2 , characterized in that an element (3) coupled to the phase element 4 is aligned relative to the beam path (2) by means of the adjustment of the actual values to the target values. Device (1) with at least one element (3), wherein a radiation is guided along a beam path (2) and detected by means of a detector (7) which has a plurality of detector elements (7.n), characterized in that - for For the purpose of aligning the at least one element (3), a phase element (4) connected to the element (3) to be aligned can be introduced into the beam path (2), in particular pivoted or pushed in, - the radiation through the action of the phase element (4) in at least two partial beams (5.1 to 5.4) are split and each of the partial beams (5.1 to 5.4) is directed onto mutually different detector elements (7.n) of the detector (7) and at least one parameter of the partial beams (5.1 to 5.4) is detected; - A control unit (10) is present which is configured in such a way that ◯ the at least one recorded parameter of the recorded partial beams (5.1 to 5.4) is recorded as an actual value and compared with a target value; ◯ current position parameters of the element (3) of the beam path (2) can be determined based on the comparison of the actual and target values with one another; and ◯ control commands are generated by means of which the current position parameter of the element (3) is influenced to align the actual values with the target values and / or necessary alignments of the actual values with the target values for an optional manual alignment on a Display (19) are shown. Device (1) according to Claim 4 , characterized in that the phase element (4) is designed as a diffractive or refractive element. Device (1) according to Claim 5 , characterized in that the phase element (4) is designed as a phase grating or a phase mask. Device (1) according to one of the Claims 4 until 6th , characterized in that the phase element (4) can be controlled. Device (1) according to one of the Claims 4 until 7th , characterized in that the element (3) can optionally be introduced into the beam path (2) and removed. Device (1) according to one of the Claims 4 until 8th , characterized in that the detector (7) remains in the beam path (2) and is set up to detect detection radiation. Phase element (4) comprising at least one structured area (16), the optical effect of which divides an impinging beam of radiation into at least two, in particular four, partial beams (5.1 to 5.4) that do not overlap one another. Phase element (4) after Claim 10 , characterized by a carrier layer (15) which has the at least one structured area (16) and at least one reference mark (17) which is used for the correct mounting of the phase element (4). Phase element (4) after Claim 11 , characterized in that the reference mark (17) is a recess in the carrier layer (15). Component (14) in the form of a wheel, a cam or a slide with a phase element (4) according to one of the Claims 10 until 12th .

Images