Phase Retrieval

Project

The phase of a field is often more important than the amplitude. This is in particular true for focusing of light.

To improve the quality of imaging it is often desirable to consider the phase in the exit pupil of the imaging system. The determination of both phase and amplitude are essential   in coherent lensless imaging.

Phase can be measured directly using interferometry, but that requires a highly stable measurement system. Alternatively one can  retrieve the phase from several intensity measurements. This is the topic of phase retrieval.


Objective

In the topic of phase retrieval the aim is to design and implement measurement systems and algorithms to compute the phase from intensity measurements. Examples are the retrieval of the phase in the exit pupil of an imaging system from through focus intensity measurements in at least two planes. Another method of phase retrieval is ptychography, where the complex transmission or reflection function of an object is retrieved from far field intensity measurements for a sequence of partial illuminations of the object.  It is also possible to use spatial light modulators to introduce a known perturbation of a field. By measuring the intensity the unknown field can be reconstructed.


Impact

Phase retrieval methods are very important in coherent imaging a very short wavelengths (e.g. EUV and x-rays)  at which no good optical components exist.

They also play an important role in 3D imaging.

 

 

 


Keywords

Projects.

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Far field nanoparticle detection

We investigate and optimize new techniques to detect nanostructures and nano-particles in semiconductor, and plastic-based fabrication technologies. The technique should be fast, operate in-line and applicable to large areas. Since the structures ...

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Wavefront coding in barcode imaging system

For simplicity, it is often assumed that the imaging system consists of a single thin lens. In the case of the barcode reader, the imaging system consists of several thick lenses and ...

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New methods and applications of Ptychography

Ptychography is a scanning Coherent Diffraction Imaging (CDI) method for reconstructing a complex valued object function from intensity measurements recorded in the Fraunhofer or Fresnel diffraction region. The technique provides a solution ...

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New methods and applications of Ptychography

Graded Index optics

Recent progress in the making of media with a variable refractive index has the potential to change lens design significantly. With these new materials, curved light rays are used to make high-quality ...

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Graded Index optics

LINX

LINX is a NWO-TTW perspective programme with the aim to apply various lensless imaging techniques, from ptychography to scatterometry, while using wavelengths in the EUV and Soft X-Ray regime. This programme is ...

project

LINX

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