ARRANGEMENT AND METHOD FOR WAVEFRONT ANALYSIS

Abstract

The present invention relates to an arrangement and to a method for wavefront analysis comprising a radiation source (8) that emits an electromagnetic wavefront of electromagnetic radiation (1) to be analyzed; a spatially resolving detector unit (4, 4a, 4b, 4c) for detecting the electromagnetic wavefront; and an electronic evaluation unit (5, 7) connected to the detector unit (4, 4a, 4b, 4c). The at least one beam guidance unit (3) for guiding the electromagnetic radiation (1), that is only diffractive and/or reflective, has at least one opening (3a, 3b, 3c) and the detector unit (4, 4a, 4b, 4c) is arranged behind the at least one opening (3a, 3b, 3c) of the beam guidance unit (3) in the direction of propagation of the electromagnetic radiation (1) for detecting a diffraction pattern of the electromagnetic radiation (1) diffracted at the at least one opening (3a, 3b, 3c).

Claims

1. An arrangement for wavefront analysis comprising a radiation source (8) that emits an electromagnetic wavefront of electromagnetic radiation (1) to be analyzed; a spatially resolving detector unit (4, 4a, 4b, 4c) for detecting the electromagnetic wavefront; an electronic evaluation unit (5, 7) connected to the detector unit (4, 4a, 4b, 4c); and at least one beam guidance unit (3) for guiding the electromagnetic radiation (1) that is only diffractive and/or reflective and that has at least one opening (3a, 3b, 3c), wherein the detector unit (4, 4a, 4b, 4c) is arranged behind the at least one opening (3a, 3b, 3c) of the beam guidance unit (3) in the direction of propagation of the electromagnetic radiation (1) to detect a diffraction pattern of the electromagnetic radiation (1) diffracted at the at least one opening (3a, 3b, 3c).

2. An arrangement in accordance with claim 1, characterized in that at least the beam guidance unit (3), the detector unit (4, 4a, 4b, 4c), or the evaluation unit (5, 7) is movable in at least two degrees of freedom relative to the radiation source (8).

3. An arrangement in accordance with claim 1, characterized in that the beam guidance unit (3), the detector unit (4, 4a, 4b, 4c), and the evaluation unit (5, 7) are arranged in a fixed position with respect to the radiation source (8).

4. An arrangement in accordance with claim 1, characterized in that the beam guidance unit (3) is formed as a spherical mirror, as an aspherical mirror, or as a free formed mirror and/or has a diffractive optical structure.

5. An arrangement in accordance with claim 1, characterized in that the at least one beam guidance unit (3) has a surface on which the electromagnetic radiation (1) is incident and which has a layer reflecting the electromagnetic radiation (1), a layer system reflecting the electromagnetic radiation (1), or a reflection hologram.

6. An arrangement in accordance with claim 1, characterized in that the at least one opening (3a, 3b, 3c) is designed in the form of a circle, of a cross, of a line, of a rectangle, of a triangle, of a trapezoid, or of a diamond.

7. An arrangement in accordance with claim 1, characterized in that the detector unit (4, 4a, 4b, 4c) and/or the beam guidance unit (3) has/have at least one cooling passage (9).

8. An arrangement in accordance with claim 1, characterized in that the detector unit (4, 4a, 4b, 4c) is formed as a position sensitive detector, as a four quadrant diode, as a CCD sensor, or as a video system.

9. A method of wavefront analysis, in which electromagnetic radiation (1) having an electromagnetic wavefront to be analyzed is emitted by means of a radiation source (8); the electromagnetic radiation (1) is guided by at least one beam guidance unit (3), that is only diffractive and/or reflective and that has at least one opening (3a, 3b, 3c), and is thus reflected and diffracted; and the electromagnetic wavefront is detected by means of a spatially resolving detector unit (4, 4a, 4b, 4c) that is arranged behind the opening (3a, 3b, 3c) of the beam guidance unit (3) in the direction of propagation of the electromagnetic radiation (1); and is evaluated with an electronic evaluation unit (5, 7) connected to the detector unit (4, 4a, 4b, 4c).

10. A method in accordance with claim 9, characterized in that at least one wavelength from the wavelength range between far ultraviolet light and infrared light is used as the electromagnetic radiation.

Description

[0021] Embodiments of the invention are shown in the drawings and will be explained in the following with reference to FIGS. 1 to 4.

[0022] There are shown:

[0023] FIG. 1 a schematic representation of an arrangement for wavefront analysis with a spherically shaped beam guidance unit;

[0024] FIG. 2 a plurality of possible forms of an opening in the beam guidance unit;

[0025] FIG. 3 a representation corresponding to FIG. 1 with a diffractive structure as a beam guidance unit; and

[0026] FIG. 4 a representation corresponding to FIG. 1 with an arrangement in which a plurality of part beams are formed.

[0027] An arrangement for wavefront analysis is shown in a schematic side view in FIG. 1. A radiation source 8 emits electromagnetic radiation 1 in the visible wavelength range between 400 nm and 780 nm. In further embodiments, the radiation source 8 can also, alternatively or additionally, emit electromagnetic radiation in the ultraviolet wavelength range or in the infrared wavelength range. The electromagnetic radiation 1 is incident as measurement light in a desired beam path on a beam guidance unit 3 designed as reflective in the embodiment shown and having an imaging effect. The beam guidance unit 3 is a spherical mirror here, but can also be an aspherical mirror or a mirror of any other desired form in further embodiments. A reflected portion 2 of the electromagnetic radiation 1 is led away for further use as a beam. A front side of the beam guidance unit 3 facing the radiation source 8 is designed such that as few optical losses as possible occur on reflection. This can take place by a correspondingly selected coating with one or more layers, that is with a layer system.

[0028] The beam guidance unit 3 has a plurality of periodically arranged holes 3a, 3b, 3c, each of the same shape and size, at which a portion of the electromagnetic radiation 1 arrives and is diffracted at the openings 3a, 3b, 3c. In further embodiments, at least one of the openings 3a, 3b, 3c, can have a size or shape differing from the other openings 3a, 3b, 3c and/or the arrangement can be aperiodic. The shape of the openings 3a, 3b, 3c is selected here such that the measurement light diffracted at the openings 3a, 3b, 3c can be analyzed with maximum information content. The size of the openings 3a, 3b, 3c is selected as so small relative to the cross-sectional surface of the incident beam of the electromagnetic radiation 1 that only very small portions of this desired wave field, i.e. of the electromagnetic radiation 1, are decoupled so that the incident electromagnetic radiation 1 is reflected largely uninfluenced by the openings 3a, 3b, 3c. Detectors 4a, 4b, 4c that together form a detector unit 4 and that are each configured as optical position sensors in the form of a PSD sensor and that are each associated with one of the openings 3a, 3b, 3c are arranged behind the beam guidance unit 3 in the direction of propagation of the electromagnetic radiation 1. In further embodiments, however, at least one of the detectors 4a, 4b, 4c can also have a type differing from the others, that is, can be a CCD detector, for example. The radiation field to be examined, i.e. the electromagnetic radiation 1 to be analyzed is redirected or deflected by means of reflection at the beam guidance unit 3.

[0029] The detector unit 4 is an analog or digital component and is electrically connected to an electronic evaluation unit 5 that receives and evaluates signals of the detector unit 4 and presents the signals of the detector unit 4 and/or the information acquired from the evaluation or analysis on an output unit, for example on a monitor or display. Parameters of an optical wavefront can thus be acquired by the shown optoelectronic arrangement directly in an imaging beam path of a desired wave field and without a use of refractive and transmitting elements (such as lenses, prisms, or beam splitter plates). A large local angular resolution can be achieved even with very highly dynamic wavefronts using the system shown.

[0030] The arrangement shown in FIG. 1 can be arranged at a fixed position with respect to the radiation source 8; however, it is also possible to mechanically or optically move the beam guidance unit 3, detector unit 4 and the electronic evaluation unit 5 or at least one of said components in at least two degrees of freedom with respect to the radiation source 8. This can take place, for example, by a design of said components arranged on a translation table having two axes of movement perpendicular to one another. A single-part design of the arrangement having components fixedly connected to one another can also be provided. Alternatively, at least one of the components of the arrangement can naturally also be designed as releasable from the remaining arrangement.

[0031] Unlike already known Hartmann-Shack systems, it is not the location of the maximum of the measurement light diffracted at the openings 3a, 3b, 3c using the arrangement shown, but rather the complete diffraction pattern of the measurement light portions that is analyzed and is registered without further optical imaging at the two-dimensional detector unit 4 that measures with spatial resolution and is analyzed by the evaluation unit 5. The wavefront or parameters of the wavefront from one or more measurements is/are modulated by the evaluation unit 5, for example using Zernike polynomials, and a complete form of the wavefront to be measured or analyzed is thus reconstructed. A direct optical imaging of a wave field to be examined in a single beam path therefore takes place. The optical arrangement shown is thus an element of in imaging beam path of an optical device.

[0032] A plurality of possible shapes of the openings 3a, 3b, 3c are shown in FIG. 2. The openings 3a, 3b, 3c can be round, ellipsoid, of cross-shape, linear, trapezoidal, diamond-shaped or can be designed in any other desired shape. Repeating features are provided with identical reference numerals in this Figure and also in the following Figures.

[0033] FIG. 3 shows in a representation corresponding to FIG. 1 a further embodiment of the arrangement in which, however, for reasons of clarity, a representation of the radiation source 8 has been omitted and now a diffractive reflective structure in the form of a hologram forms the beam guidance element 3 instead of a spherical mirror. In addition, a cooling passage 9 is now arranged at a rear side of the beam guidance element 3 remote from the radiation source 8; it equally contacts the detector unit 4 and is intended to discharge heat arising by incidence on the electromagnetic radiation 1 at the components in direct contact with it, that is at the beam guidance unit 3 and the detector unit 4. The cooling passage 4 can naturally equally also be used in the further embodiments shown.

[0034] A further embodiment is shown in FIG. 4, with in this case the electromagnetic radiation 1 transmitted by the radiation source 8 (not shown for reasons of clarity) and incident on the beam guidance unit 3 is split by the beam guidance unit 3 after decoupling of the measurement light incident on the detector unit 4 into two reflected part beams that are each incident on a beam absorber 6 via a mirror system 7a, 7b.

[0035] In a further embodiment, the radiation field to be analyzed, i.e. the electromagnetic radiation 1, can also be directly incident on a beam trap that is provided with cooling apparatus to dissipate the energy of the radiation field.

[0036] Features of the different embodiments only disclosed in the embodiment examples can be combined with one another and claimed individually.