Matched-filtering generalized phase contrast using LCoS pico-projectors for beam-forming

Abstract

Abstract:We report on a new beam-forming system for generating high intensity programmable optical spikes using so-called matched-filtering Generalized Phase Contrast (mGPC) applying two consumer handheld picoprojectors. Such a system presents a low-cost alternative for optical trapping and manipulation, optical lattices and other beam-shaping applications usually implemented with high-end spatial light modulators. Portable picoprojectors based on liquid crystal on silicon (LCoS) devices are used as binary phase-only spatial light modulators by carefully setting the appropriate polarization of the laser illumination. The devices are subsequently placed into the object and Fourier plane of a standard 4f-setup according to the mGPC spatial filtering configuration. Having a reconfigurable spatial phase filter, instead of a fixed and fabricated one, allows the beam shaper to adapt to different input phase patterns suited for different requirements. Despite imperfections in these consumer picoprojectors, the mGPC approach tolerates phase aberrations that would have otherwise been hard to overcome by standard phase projection.

Optical cell sorting with multiple imaging modalities

“…This also leads to a safer operation of the device. Other efficient light shaping methods such as GPC 12,13 or matched filtering GPC 14,15 can be incorporated later due to the modular approach of the cell-BOCS's the laser beam shaping engine. Laser light (λ=1070nm) that is shaped by the SLM is subsequently focused into the microfluidic chip at locations determined using computer vision.…”

GPC light shaper for speckle-free one- and two-photon contiguous pattern excitation

“…These low frequency perturbations reemerge at the output as light outside the desired shape. With an idea of how the Fourier distribution should look like, we thus adopt how DH applies phase constraints to get a desired Fourier transform output [29], or how matched filtering GPC uses concentric rings to emulate plane wave focusing and, consequently, output focal spots [30]. For the circular pattern, the deviations from the ideal Airy-like function are minimized when the PCF's radius coincides with the zero crossing at the central region at the Fourier plane.…”

Robust and Low-Cost Light Shaping

“…Using two modified pocket pico-projectors, we have demonstrated beam shaping based on matched filtering generalized phase contrast (mGPC). 4 One projector is encoded with dynamic correlation target phase patterns that are directly mapped into intensity spikes. The other projector acts as a tunable matched filter combining GPC and phase-only correlation.…”

“…The correlation pattern and filter can be optimized to increase the space bandwidth, thus producing narrower, more intense output spikes. 4 …”