X-ray Phase-Contrast Imaging and Metrology through Unified Modulated Pattern Analysis

Abstract

We present a method for x-ray phase-contrast imaging and metrology applications based on the sample-induced modulation and subsequent computational demodulation of a random or periodic reference interference pattern. The proposed unified modulated pattern analysis (UMPA) technique is a versatile approach and allows tuning of signal sensitivity, spatial resolution, and scan time. We characterize the method and demonstrate its potential for high-sensitivity, quantitative phase imaging, and metrology to overcome the limitations of existing methods.

State of the Art of X-ray Speckle-Based Phase-Contrast and Dark-Field Imaging

“…As the speckles have an irregular, random shape and a distribution of sizes, only an average speckle size can be estimated. This is done for example by determining the spatial frequency at the maximum of the power spectrum [86,87,123,129] or from a 2D auto-correlation of the speckle pattern [88,128,[130][131][132][133][134]. Generally, well-defined, small speckles that can be resolved easily and cover a few pixels in the detector plane are desired.…”

Applications of Laboratory-Based Phase-Contrast Imaging Using Speckle Tracking Technique towards High Energy X-Rays

“…[33]. The spatial resolution for speckle tracking technique here is largely limited by the correlation window size but can be largely improved by using extra stages to scan the wavefront modulator, e.g., in 1D, 2D raster or a non-gird scheme [26,39,40]. The speckle size and visibility also affect the spatial resolution and noise level [24,25], which can be adjusted by changing to different diffusers for other applications.…”

3d virtual histology of neuronal tissue by propagation-based x-ray phase-contrast tomography

“…As the phase shift is not directly measurable, it has to be converted to object specific modulations in the intensity images. For this purpose various methods exist as, e.g., zone-plate microscopes with Zernike phase contrast [26,151,159], Talbot interferometry [111,134,152,188], edge illumination [64,116] or speckle-based imaging [13,113,199], which are all full-field imaging techniques. In contrast to scanning techniques like ptychography [36,72,189] acquisition time is significantly reduced which is an important factor in tomographic imaging, requiring several projection images of the sample from different angles, especially with regard to the stability of degrading biological specimens.…”

“…Compared to other techniques, they provide a very high density resolution with accurately retrieved values of the complex index of refraction [197]. However, spatial resolution is limited to the range of few micrometers [137,197,199] and phase-stepping is necessary for high quality reconstructions, although also single-step approaches have been proposed, leading to the need of additional a priori knowledge or a decrease in spatial resolution [14,15,196]. Moreover, in Talbot interferometry and edge illumination radiation dose is increased due to absorbing optical elements behind the sample and imperfections in these elements as well as their alignment might alter the reconstruction quality [197].…”