Dual-channel low-coherence interferometry and its application to quantitative phase imaging of fingerprints

Abstract

We introduce an off-axis, wide-field, low-coherence and dual-channel interferometric imaging system, which is based on a simple-to-align, common-path interferometer. The system requires no optical-path-difference matching between the interferometric arms in order to obtain interference with low-coherence light source, and is capable of achieving two channels of off-axis interference with high spatial frequency. The two 180°-phase-shifted interferograms are acquired simultaneously using a single digital camera, and processed into a single, noise-reduced and DC-suppressed interferogram. We demonstrate using the proposed system for phase imaging of fingerprint templates. Due to the fact that conventional phase unwrapping algorithms cannot handle the complex and deep surface topography imposed by fingerprint templates, we experimentally implemented two-wavelength phase unwrapping using a supercontinuum laser coupled to acousto-optical tunable filter, together functioning as a low-coherence tunable light source. From the unwrapped phase map, we produced high quality depth profiles of fingerprint templates.

Investigation of 3D surface acoustic waves in granular media with 3-color digital holography

“…In the past decade, digital holographic imaging has been developed at an accelerating pace and impacted a wide range of domains, such as microscopy [1][2][3][4][5][6][7][8][9][10][11] fluid mechanics, 12,13 or photomechanics. 14,15,17 Phase imaging measures the optical path length map associated with transparent specimens (transmission illumination) or opaque surfaces (reflection illumination) and translates these data into relevant information.…”

“…14,15,17 Phase imaging measures the optical path length map associated with transparent specimens (transmission illumination) or opaque surfaces (reflection illumination) and translates these data into relevant information. Information can be of various nature, such as biomedical, 3,4,7,8 topology at nanoscale, 5,11 flows and vortices, 13,14 material properties, 15,16 surface shape, 17 polarization, 18 displacement field, 19,20 or vibrations. [21][22][23][24] Recently, a real-time three-dimensional deformation measurement based on threecolor digital Fresnel holography and simultaneous recording with a color sensor was demonstrated.…”

Quantitative phase imaging in flows with high resolution holographic diffraction grating

“…In the past years, quantitative phase imaging was developed and dedicated to a wide range of applications [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Phase measurement deals with the optical path length related to propagation inside transparent specimens (transmission illumination) or to reflection on opaque surfaces (reflection illumination), and translates this data into relevant information.…”

Flipping interferometry with doubled imaging area

“…Furthermore, even if using contrast agents in flow cytometry, the fact that the phase profile is quantitative and accounts for the cell internal refractive indices gives rise to new parameters with medical relevance, which were not available in flow cytometry before, such as the dry mass of the cell. Off-axis holography [1][2][3] captures the complex wavefront of the sample within a single camera exposure, by inducing a small angle between the sample and reference beams creating the interference pattern of the hologram, which is highly relevant for quantitatively acquiring dynamic samples. This single-exposure mode is possible since the sample complex wavefront is fully separated from the other terms in the spatial frequency domain.…”