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Schematic diagram illustrating the principle of z-microscopy.
Numerical analysis of the system impulse response (a) Schematic diagram of the simulation model: a converging wave is diffracted by an array of ten micro mirrors; (b) Normalized power collected by each micro mirror when a converging beam is focused on the target mirror (i.e., the 5th micro mirror); (c) Intensity distribution (in logarithmic scale) in the x-z axial slice plane showing the diffraction of a converging beam by the micro mirror array; Strong diffraction occurs at the target mirror (5th mirror) where the beam is focused at; The reflected wave is not tracked in the calculation and assumed to be completely detected; (d) Simulated impulse response; The horizontal axis denotes the position at which the probe beam is focused (i.e., the geometric image position of the point source probe) while the vertical axis represents the normalized power detected by each detector; Each curve corresponds to the response of a different detector.
Fabricated micro mirror array; (a) Optical microscope image of an array of micro mirrors standing on a silicon substrate; (b) Top view microscope (NIKON L200ND) image of the micro mirror array. The mirrors are tilted by 45° with respect to the light incidence direction. (c) A scanning electron microscope (FEI Philips XL-20 SEM) image showing two adjacent micro mirrors.
(a) Schematic diagram of the experimental setup; (b) Chromatically extended depth of focus; Different wavelengths of the excitation pulse are focused to different axial positions due to purposely introduced chromatic aberration; (c) Z-imaging by using a micro mirror array; Micro mirrors are tilted at 45° with respect to the axial direction to de-multiplex fluorescence signals excited at different axial positions for parallel detection. (d) Depth response measured by scanning a 2-μm fluorescent microsphere along the axial direction. Each row of the figure is a line image acquired when the microsphere probe was at an axial position specified by the vertical axis. White dotted line shows the depth position—mirror number mapping relationship, indicating an effective axial separation of about 3.3 μm in the sample space between two adjacent micro mirrors. (e) Normalized micro-mirror depth response (averaged over multiple mirrors), error bars indicate the standard deviation.
Z-imaging experimental results (a) Micrograph of the sample (i.e., multiple microspheres) used in the experiment; One microsphere is located at a very different depth level; (b) Artistic schematic showing multiple axial planes imaged in parallel by the micro mirror array; (c)-(f): Imaging results at four axial positions obtained by using the micro mirror array; Microspheres at different depths are resolved; The optical sectioning ability of the imaging system can be observed as the out-of-focus fluorescence signal is significantly suppressed [see (a) and (f)].
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