# Microparticle Manipulation and Imaging through a Self-Calibrated Liquid Crystal on Silicon Display
###### Abstract
For the surface profile calibration case, a highly collimated beam illuminates the LCoS display where an S-H configuration has been implemented. After reflection on the LCoS display, the input light creates a spot array distribution at the micro-lens focal plane. If the input light is highly collimated, light dots deviations from a reference dots-pattern are mainly originated by inhomogeneity at the LCoS screen. At this moment, by calculating the deviation of each individual spot to its theoretical center, the surface profile can be accurately retrieved by using numerical methods. Once the LCoS display is optimized, we use it for optical applications. Two different applications we recently developed for microparticles imaging [23; 24] and manipulation [12; 13] are revised in this manuscript. First, we use such elements to realize customized three-dimensional light structures. Due to photophoretic force fields [25] associated to created light structures, we conduct microparticle spatial trapping and manipulation, being useful to investigate physical or biological phenomenon of molecules [26], atoms [27], or even cells [28]. To obtain such light trapping architecture, we propose split-lens inspired configurations addressed to the LCoS display. Second, we propose an inline (IL) optical arrangement to perform dynamic holographic imaging of microparticles (placed to arbitrary spatial positions). In particular, this IL system is based on LCoS device used to generate a double-sideband filter, to be applied at the Fourier plane of the holographic system [29]. Under this scenario, the undesired conjugate image (ghost image) is dynamically eliminated by the double-sideband filter. When compared with other proposals, our optical arrangement presents significant advantages, as the elimination of ghost images into an inline and robust configuration, and without the necessity of time-sequential measurements. The outline of this review is as follows. In the Materials and Methods section, we preliminarily demonstrate the LCoS display calibration technique, with special focus on the phase-voltage relation calibration and the surface homogeneity determination. We also provide the use of this device to implement an optical architecture to realize particle trapping and manipulation. Finally, this section also presents the description and the usage of the double-sideband filter based inline holographic system, for microparticles holographic imaging. In the Results section, we show the experimental results obtained for the three methods described. We firstly present the LCoS display self-calibration results, for the phase-voltage look-up table and the LCoS screen profile. Afterwards, we show the experimental realization of microparticles trapping and spatial control with this calibrated LCoS display. Finally, by registering the LCoS display into the IL holographic architecture, we demonstrate the real-time holographic imaging of microparticles which are located in different spatial positions. In the Conclusion section, we highlight the important role of the LCoS display in the diverse methods proposed.