Measuring device and methods for characterization of a radiation field

Abstract

A radiation field measuring device for the characterization of a radiation field is disclosed. The measuring device may include a detector device and a reconstruction device. The detector device may have at least one detector camera, which contains at least one detector array arranged for the image recording of scattered radiation in a multiplicity of lateral directions that deviate from the longitudinal direction. The reconstruction device may be configured for the tomographic reconstruction of a field density of the scattered radiation in the radiation field.

1 - 31 . (canceled) 
     
     
         32 . A method for characterizing a radiation field ( 1 ) that passes through a medium ( 2 ) in a longitudinal direction (z), using a radiation field measuring device ( 100 ), comprising the steps:
 recording an image, by means of a detector device ( 10 ), of scattered radiation ( 3 ), which is generated in the medium ( 2 ) by the radiation field ( 1 ) and is directed in a multiplicity of lateral directions that deviate from the longitudinal direction (z), and   characterizing of the radiation field ( 1 ) with a reconstruction device ( 20 ) using image signals of the detector device ( 10 ), wherein   reconstructing the image with the reconstruction device ( 20 ) carries out a tomographic reconstruction of a field density of the scattered radiation ( 3 ) in the radiation field ( 1 ).   
     
     
         33 . The method according to  claim 32 , in which
 the reconstruction device ( 20 ) carries out a non-analytical, in particular statistical or algebraic, tomographic reconstruction of the field density of the scattered radiation ( 3 ).   
     
     
         34 . The method according to  claim 33 , in which
 the reconstruction device ( 20 ) carries out the tomographic reconstruction of the field density of the scattered radiation ( 3 ) by means of an iterative algorithm.   
     
     
         35 . The method according to  claim 33 , in which
 the reconstruction device ( 20 ) carries out a statistical tomographic reconstruction of the field density of the scattered radiation ( 3 ), wherein   the statistical tomographic reconstruction is based on a statistical model with an objective functional to be minimized, the tomographic data mismatch term of which accounts for the noise characteristics of the measurement data.   
     
     
         36 . The method according to  claim 35 , in which
 the objective functional contains an Lp-norm term with (0≤p< 2 ) and/or a Bayesian regularization term.   
     
     
         37 . The method according to  claim 32 , in which
 the image recording of scattered radiation ( 3 ) takes place such that the lateral angles are distributed in such a way that the components of the recorded scattered radiation ( 3 ) running perpendicular to the longitudinal direction (z) span a measurement range of 180° to 360°.   
     
     
         38 . The method according to  claim 37 , in which
 the image recording of scattered radiation ( 3 ) takes place such that the components of the recorded scattered radiation ( 3 ) running perpendicular to the longitudinal direction (z) are unevenly distributed in the case of an even number of lateral directions and a measurement range over 360°, and evenly distributed otherwise.   
     
     
         39 . The method according to  claim 32 , in which
 the image recording of scattered radiation ( 3 ) takes place in at least 2 lateral directions, in particular at least 3 lateral directions, and/or   the image recording takes place in a spectrally selective manner.   
     
     
         40 . The method according to  claim 32 , in which
 the field density of the scattered radiation ( 3 ) is reconstructed in the forward and backward projection process of the tomographic reconstruction, with an illumination background of the radiation field ( 1 ) taken into account.   
     
     
         41 . The method according to  claim 32 , comprising the steps
 tomographic reconstruction of a layer section of the field density of the scattered radiation ( 3 ), and   conversion of the field density of the scattered radiation ( 3 ) into a two-dimensional intensity distribution of the radiation field ( 1 ).   
     
     
         42 . The method according to  claim 32 , comprising the step
 tomographic reconstruction of a field density of the scattered radiation ( 3 ) in a three-dimensional volume section, which comprises at least two juxtaposed layer sections.   
     
     
         43 . The method according to  claim 32 , comprising the step
 deflection of the scattered radiation ( 3 ) along the multiplicity of lateral directions with the deflector device ( 30 ) onto the at least one detector camera ( 11 ).   
     
     
         44 . The method according to  claim 32 , comprising the steps
 rotation of the radiation field ( 1 ) about the longitudinal direction (z) with the beam rotator, and   image recording of the scattered radiation ( 3 ) with a single detector camera ( 11 ), wherein   for the image recording of scattered radiation ( 3 ) in the multiplicity of lateral directions, the radiation field ( 1 ) is rotated with the beam rotator into different rotational positions relative to the detector camera ( 11 ).   
     
     
         45 . The method according to  claim 32 , comprising the step
 ascertaining an intensity distribution of the radiation field ( 1 ) on the basis of the reconstructed field density of the scattered radiation ( 3 ).   
     
     
         46 . The method according to  claim 32 , comprising the step of capturing at least one of the beam parameters, which comprise
 pulse energy or pulse energy density of the radiation field ( 1 ) in the case of a pulsed radiation field ( 1 ),   field density of the radiation field ( 1 ) in the case of a continuous radiation field ( 1 ),   geometric properties of the radiation field ( 1 ), in particular beam diameter, divergence angle and/or beam shape,   properties of the beam waist of the radiation field ( 1 ), in particular radius, position along the longitudinal direction (z), and/or shape of the focus in transaxial section,   spatial location of the radiation field ( 1 ) in the medium ( 2 ),   coherence properties of the radiation field ( 1 ),   wave fronts of the radiation field ( 1 ),   Rayleigh lengths of the radiation field ( 1 ), and   diffraction indexes, M 2  and beam propagation factors k of the radiation field ( 1 ).   
     
     
         47 . The method according to  claim 45 , in which
 provision is made for continuous capturing of the at least one beam parameter and the temporal stability thereof.   
     
     
         48 . The method according to  claim 45 , comprising the step
 calculation of a beam propagation, in particular by means of wave front analysis.   
     
     
         49 . The method according to  claim 48 , comprising the step
 calculation of a focus position of the radiation field ( 1 ).   
     
     
         50 . The method according to  claim 32 , in which
 the field density of the scattered radiation ( 3 ) is reconstructed with particles in the medium taken into account, which particles would lead to artefacts of the reconstructed field density if they were not taken into account.   
     
     
         51 . The method according to  claim 50 , in which
 provision is made for a serial image recording, which comprises a plurality of sequential image recordings, and   artefact-bearing scatter events, which arise from particles in the medium, are eliminated by an analysis of the serial image recording.   
     
     
         52 . The method according to  claim 32 , comprising the step
 providing the medium ( 2 ) in the radiation field measuring device in a particle-free state.   
     
     
         53 . The method according to  claim 32 , comprising the step
 capturing a volumetric particle distribution in the radiation field ( 1 ).   
     
     
         54 . The method according to  claim 32 , comprising the steps
 monitoring and/or controlling a radiation source with which the radiation field ( 1 ) is generated.   
     
     
         55 . The method according to  claim 54 , in which
 the radiation source is used for laser-supported material processing in cutting and joining technologies or in manufacturing in semiconductor technology, or in therapy and/or surgery by means of laser radiation.   
     
     
         56 . The method according to  claim 54 , in which
 the radiation source contains a setting device with which the beam parameters of the radiation field ( 1 ) can be varied, wherein   the setting device is controlled according to an intensity profile of the radiation field ( 1 ) along the longitudinal direction (z), more particularly in the focus of the radiation field ( 1 ).   
     
     
         57 . The method according to  claim 54 , in which
 the radiation source contains a focusing device, and   the focusing device is controlled according to the position of the focus along the longitudinal direction (z).