Abstract
This paper investigates experimental means of measuring the transmission matrix (TM) of a highly scattering medium, with the simplest optical setup. Spatial light modulation is performed by a digital micromirror device (DMD), allowing high rates and high pixel counts but only binary amplitude modulation. On the sensor side, without a reference beam, the CCD camera provides only intensity measurements. Within this framework, this paper shows that the TM can still be retrieved, through signal processing techniques of phase retrieval. This is experimentally validated on three criteria : quality of prediction, distribution of singular values, and quality of focusing.
Highlights
Wave propagation in complex media is a fundamental problem in physics, be it in acoustics, optics, or electromagnetism [1]
In this work we report on the full measurement of the complex transmission matrix (TM) of a multiply scattering medium, using a digital micromirror device (DMD) binary amplitude modulator as an spatial light modulators (SLM), with no reference on the detection side, as shown on Fig. 1(c)
This paper shows that the full complex-valued transmission matrix of a strongly scattering material can be estimated, up to a global phase factor on each of its rows, with a simple experimental setup involving only real-valued inputs and outputs
Summary
Wave propagation in complex media is a fundamental problem in physics, be it in acoustics, optics, or electromagnetism [1]. Ferent wavefront shaping approaches rely on digital phase-conjugation [3, 4] or iterative algorithms [5], but it is possible to measure the so-called transmission matrix (TM) of the medium [6], which fully describes light propagation through the linear medium, from the modulator device to the detector This approach has been efficient for focusing, imaging [7, 8] and for studying the transmission modes of the medium [9]. In this work we report on the full measurement of the complex TM of a multiply scattering medium, using a DMD binary amplitude modulator as an SLM, with no reference on the detection side, as shown on Fig. 1(c) This approach combines the high-speed and high pixel counts allowed by DMD devices, with the simplicity and robustness of a reference-less optical setup. Beam-splitter DMD Scattering Beam-splitter medium b) Phase and amplitude shaping by Lee hologram and Fourier filtering
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