Each micromirror represents a single pixel of the projected image. DMD consists of a CMOS-placed micromirrors array, each of which can have only two stable states: “On” ( \(+12^\)) 22. This is particularly relevant in biomedical applications where rapid processes are involved, or the possibility of real-time measurement should be provided 11, 22, 26. It provides a high enhancement factor in the task of focusing through the scattering medium 19 or improving contrast and beam-shaping fidelity in optical imaging 20. Over the past few years, such devices have been actively used in various studies 11, 22, and commercial devices (e.g., holotomographic microscope HT-1H, developed by Tomocube, Inc). Compared to other modulators, DMD has a high switching speed, a high fill-factor (90%), and a relatively low cost 23, 24, 25. In addition, DMD constructively assumes only binary modulation. In applications where high speed is required and spatial resolution can be sacrificed to achieve high light modulation rates, the use of DMD is preferable due to its high refresh rate 22. Several important characteristics of wavefront modulators can be highlighted: the speed of operation, modulation dynamic range, number and size of pixels, and modulation efficiency. The choice of the required device is determined by the peculiarities of the problem to be solved in a particular case. Different types of modulators were compared, based on which the advantages and disadvantages of each technique were identified 18, 19, 20, 21. MEMS-based spatial light modulators are presented by a digital micromirror device (DMD), an active micromirror matrix, and a grating light valve 18.Įach of the devices is characterized by the type of modulation, among which they can be distinguished: amplitude-only, phase-only, and simultaneous amplitude-phase modulation. The former includes such subtypes as transmissive liquid crystal, reflective liquid crystal on silicon, and ferroelectric liquid crystal. Two major types of such devices can be outlined: liquid crystal-based spatial light modulators and micro-electromechanical systems (MEMS). Adaptive spatial light modulators with programmable precise control of the wavefront have become a valuable tool for various applications, e.g., in imaging systems 17. To date, there exists a range of static and dynamic wavefront modulators, such as diffraction optical elements 12, metasurfaces 13, adaptive optical elements 14, which provide the possibility to operate with the amplitude, phase, or polarization of the beam profile in a wide range of wavelengths 15, 16. Some of the applications of wavefront shaping are high-resolution microscopy 1, laser beam shaping 2, 3, scattering media characterization 4, 5, 6, holographic displays 7, quantum cryptography 8, metrology 9, compressed sensing 10, 3D bioprinting and lithography 11. The synthesis of wavefronts with known characteristics has attracted the interest of many researchers in the field of photonics. The results of the study will greatly contribute to the improvement of modulated wavefront quality in various applications with different requirements for spatial resolution and quantization. The algorithm takes into account the type of modulation, that is, amplitude, phase, or amplitude-phase, the size of the encoded distribution, and its requirements for spatial resolution and quantization. Based on a statistical analysis of the data, an algorithm for selecting parameters (carrier frequency of binary pattern and aperture for the first diffraction order filtering) that ensures the optimal quality of the modulated wavefront was developed. The study aims to investigate the spatial resolution and quantization achievable using this approach and its optimization based on the parameters of the target complex wave and the modulation error estimation. The paper presents the results of a comprehensive study on the optimization of independent amplitude and phase wavefront manipulation which is implemented using a binary digital micromirror device.
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