Device and method for microstructuring a storage medium and storage medium comprising a microstructured region

Abstract

A device providing for microstructuring a storage medium includes a radiation source for producing an at least partially coherent beam from electromagnetic radiation, a modulator-provided with a plurality of individually switchable modulator elements, a beam-forming optical element for illuminating the modulator, a reducing optical element for reducing a beam radiated by the modulator, and a transport table for displacing the storage medium in relation to the reducing optical element. The device solves technical problems caused by writing of microstructuring and individual diffractive optical elements, in particular computer-generated holograms having a high speed and high writing energy. The device is achieved in that the reducing optical element is configured with limited diffraction and produces a surface reduction of at least 25 from a surface of the individually switchable modulator elements.

1 . A device for autofocusing an imaging optical unit of a writing device for microstructuring a storage medium, wherein a distance and/or a tilting of the imaging optical unit relative to the storage medium is regulated, comprising:
 at least two light sources,   at least one beam splitter for directing light beams generated by the at least two light sources onto the imaging optical unit,   at least two detectors for analyzing light beams reflected by the storage medium,   at least one beam splitter for directing a light that is reflected by the storage medium and runs through the imaging optical unit onto the at least two detectors, and   a lens for focusing the light reflected by the storage medium onto the at least two detectors.   
   
   
       2 . The device as claimed in  claim 1 ,
 wherein one of the at least two detectors is assigned to each of the at least two light sources.   
   
   
       3 . The device as claimed in  claim 1 ,
 wherein the at least two detectors are formed as a 4-quadrant detector, and   wherein at least one optical element that generates an astigmatism is assigned to each of the at least two detectors.   
   
   
       4 . The device as claimed in  claim 1 ,
 wherein the at least two light sources and the at least two detectors are provided with actuators for alternating a spatial position.   
   
   
       5 . A method for autofocusing an imaging optical unit of a writing device for microstructuring a storage medium, wherein a distance of the imaging optical unit relative to the storage medium is regulated, wherein
 light beams are generated by at least two light sources and directed onto the imaging optical unit,   the light beams are focused onto a surface of the storage medium at a scanning point and reflected by the storage medium,   focus error signals are generated by at least two detectors for analyzing light beams reflected by the storage medium,   a light that is reflected by the storage medium and runs through the imaging optical unit is directed onto the at least two detectors by at least one beam splitter,   the light reflected by the storage medium is focused onto the at least two detectors, and   regulation of the distance of the imaging optical unit relative to the storage medium is carried out in a manner dependent on the focus error signal of at least one of the at least two detectors.   
   
   
       6 . The method as claimed in  claim 5 , wherein each reflected light beam is analyzed by an assigned detector. 
   
   
       7 . The method as claimed in  claim 5 , wherein a regulation is carried out with at least two light beams spatially and/or temporally independently of one another. 
   
   
       8 . The method as claimed in  claim 5 , wherein
 with the aid of the writing device, a writing beam is focused onto the surface of the storage medium for producing a micro structuring,   an areal microstructuring is produced by a relative movement between the imaging optical unit and the storage medium, and   depending on a direction of movement, at least one scanning point which is positioned before the writing beam in the direction of movement is produced on the surface of the storage medium.   
   
   
       9 . The method as claimed in  claim 5 , wherein an exposure line is produced as focused writing beam. 
   
   
       10 . A method for autofocusing an imaging optical unit of a writing device for microstructuring a storage medium, wherein a distance and a tilting of the imaging optical unit relative to the storage medium are regulated, wherein
 a light beam is generated by at least one light source and directed onto the imaging optical unit,   the light beam is directed onto a surface of the storage medium and reflected by the storage medium,   the distance between the imaging optical unit and the surface of the storage medium is determined at least two points of the surface, and   measured distances are used to determine and regulate the distance and the tilting.   
   
   
       11 . The method as claimed in  claim 10 , wherein
 with the aid of the writing device, a writing beam is focused onto the surface of the storage medium for producing a micro structuring,   an areal microstructuring is produced by a relative minimum between the imaging optical unit and the storage medium, and   a region illuminated by the light beam is positioned before the writing beam in a direction of movement.   
   
   
       12 . The method as claimed in  claim 10 , wherein
 at least two light beams are focused onto the surface of the storage medium at scanning points,   a focus error signal is generated by at least two detectors for analyzing the at least two light beams that are reflected by the storage medium,   for scanning points, the distance between the imaging optical unit and the surface of the storage medium is determined from the focus error signals, and   a correction of the tilting of the storage medium relative to the imaging optical unit is carried out depending on the focus error signals for the scanning points.   
   
   
       13 . The method as claimed in  claim 10 , wherein
 the light beam is focused onto the surface of the storage medium at a scanning point and reflected by the storage medium,   a focus error signal is generated by a detector for analyzing the light beams reflected by the storage medium,   the scanning point is scanned over a section of the surface of the storage medium, and   a distance profile is produced from measured focus error signals.   
   
   
       14 . The method as claimed in  claim 10 , wherein a scanning direction is oriented transversely with respect to a direction of a relative movement between the imaging optical unit and the storage medium. 
   
   
       15 . The method as claimed in  claim 10 , wherein
 the light beam is directed onto the surface of the storage medium and reflected by the storage medium, and   the distance between the imaging optical unit and the storage medium is determined at a plurality of points by a wavefront detector for analyzing the light beams reflected by the storage medium.   
   
   
       16 . A method for determining an operating point of a device for autofocusing an imaging optical unit of a writing device for microstructuring a storage medium, wherein a distance and/or a tilting of the imaging optical unit relative to the storage medium is regulated, wherein
 a predetermined region of a surface of the storage medium is structured with a predetermined pattern,   along one axis an intensity and along the other axis an exposure height are altered continuously, and   afterward an exposed region is analyzed microscopically and the operating point is defined.   
   
   
       17 . The method as claimed in  claim 16 , wherein
 a value range of 16 different gray shades is used for the intensity, and   the exposure height is varied over a region of a predetermined S curve.   
   
   
       18 . The method as claimed in  claim 16 , wherein an optimum exposure height where a structuring is sufficiently achieved with extremely low intensity of a writing beam is established for a setting. 
   
   
       19 . The method as claimed in  claim 16 , wherein a focus error signal is used as a reference for the exposure height. 
   
   
       20 . The method as claimed in  claim 16 , wherein a focus error signal is used as a reference for the operating point.