This Letter develops a framework for digital holography at optical wavelengths by merging phase-shifting interferometry with single-pixel optical imaging based on compressive sensing. The field diffracted by an input object is sampled by Hadamard patterns with a liquid crystal spatial light modulator. The concept of a single-pixel camera is then adapted to perform interferometric imaging of the sampled diffraction pattern by using a Mach-Zehnder interferometer. Phase-shifting techniques together with the application of a backward light propagation algorithm allow the complex amplitude of the object under scrutiny to be resolved. A proof-of-concept experiment evaluating the phase distribution of an ophthalmic lens with compressive phase-shifting holography is provided.
We demonstrate imaging of complex amplitude objects through digital holography with phase-structured illumination and bucket detection. The object is sampled with a set of micro-structured phase patterns implemented onto a liquid-crystal spatial light modulator while a bucket detector sequentially records the irradiance fluctuations corresponding to the interference between object and reference beams. Our reconstruction algorithm retrieves the unknown phase information from the full set of photocurrent measurements. Interestingly, the sampling functions can be codified onto the reference beam, so they can be nonlocal with respect to the object. Finally, we show that the system is well-fitted for transmission of the object information through scattering media.
Abstract:We provide experimental measurement of the Mueller matrices corresponding to an on-state liquid-crystal-on-silicon display as a function of the addressed voltage. The polar decomposition of the Mueller matrices determines the polarization properties of the device in terms of a diattenuation, a retardance and a depolarization effect. Although the diattenuation effect is shown to be negligible for the display, the behavior of the degree of polarization as a function of the input polarization state shows a maximum coupling of linearly polarized light into unpolarized light of about 10%. Concerning the retardation effect, we find that the display behaves as a retarder with a fast-axis orientation and a retardance angle that are voltage-dependent. The above decomposition provides a convenient framework to optimize the optical response of the display for achieving a phase-mostly modulation regime. To this end, the display is sandwiched between a polarization state generator and a polarization state analyzer. Laboratory results for a commercial panel show a phase modulation depth of 360º at 633 nm with a residual intensity variation lower than 6 %.
We present a method for recording in-line single-shot digital holograms based on the fractional Talbot effect. In our system, an image sensor records the interference between the light field scattered by the object and a properly codified parallel reference beam. A simple binary twodimensional periodic grating is used to codify the reference beam generating a periodic three-step phase distribution over the sensor plane by fractional Talbot effect. This provides a method to perform single-shot phase-shifting interferometry at frame rates only limited by the sensor capabilities. Our technique is well adapted for dynamic wavefront sensing applications. Images of the object are digitally reconstructed from the digital hologram. Both computer simulations and experimental results are presented.
It is shown for the first time we believe, that when a spherical wave illuminates a certain type of diffracting screen, in addition to the expected focal-shift effect, depending on the value of the Fresnel number of the focusing system, a focal switch effect can appear, i.e., an increase in the height of the lateral lobe of the axial-intensity distribution over that of the central lobe.
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