The literature deals with the modulation transfer function (MTF) only for object brightness distribution functions (OBDFs) oriented along the meridional and sagittal directions. This paper addresses computation of the geometrical MTF for an off-axis source point when the OBDF is oriented along any arbitrarily defined direction. This study finds that the MTF is not a monotonic increasing or decreasing function when the direction of the OBDF is changing. Consequently, the extreme MTF values may occur when the OBDF is aligned at any direction between the meridional and sagittal directions. Four theorems are provided for the MTF and the phase shift variations that take place when the OBDF is translated or rotated. It is found that the MTF and the phase shift are symmetrical or antisymmetrical about certain directions. Thus, to observe all possible changes in the MTF and the phase shift, it is sufficient to rotate the OBDF through a range of just 90°. The presented method is based on a recent irradiance method for MTF computation that does not rely on counting the number of ray hits on a mesh, making the method immune to effects of grid size and thus improving traditional accuracy.
This study describes an electrically tunable two-dimensional (2D) liquid crystal holographic polarization grating. It is a twisted nematic grating array, which is obtained by orthogonally overlaying two crossed one-dimensional (1D) polarization holograms. A 1D polarization hologram has a rotating linear polarization pattern, generated by the interference of two orthogonal circularly polarized beams on a substrate that is coated with an azo-dye-doped polyvinyl alcohol layer. The images under a polarized optical microscope and the diffraction patterns from the 2D grating are simulated using the Jones matrix and a Fourier transformation. The experimental results agree with the simulated results. This work represents a substantial advance toward the realization of highly functionalized passive optical devices in which both the beam propagation direction and the polarization state can be controlled in two dimensions.
The paper proposed novel designs to pinch the transverse diffusion of the sample in the injection mode using microelectrodes to generate the potential difference at the channel intersection in the capillary electrophoresis (CE) microchip. A pair of microelectrodes was used to conduct the injection channel and the separation channel, which directly provided the potential to pinch the sample without using a power supply. These new designs of the CE microchip simplify the electric circuitry and improve performance. Simulations were performed using the CFD-ACE[trade mark sign] software. The mechanisms of diffusion and electrophoresis were employed in the numerical simulation. The injection and separation processes of the sample were simulated and the parameters of the present design were investigated numerically.
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