45.5X Infinity Corrected Schwarzschild Microscope Objective Lens Design

In this article, the design of a 45.5X (numerical aperture (NA) =0.5) infinity corrected, or infinite conjugate, Schwarzschild reflective microscope objective lens is discussed. Fast Fourier transform modulation transfer function (FFT MTF= 568.4 lines/mm at 50% contrast for the on-axis field-of-view), root-mean-square wavefront error (RMS WFE= 0.024 waves at 700 nm), point spread function (PSF, Strehl ratio= 0.972), encircled energy (0.88 µm spot radius at 80% fraction of enclosed energy), optical path difference (OPD=-0.644 waves) and Seidel coefficients calculated with Zemax® are provided to show that the design is diffraction-limited and aberration-free. Furthermore, formulas expressing the relationship between the parameters of the two spherical mirrors and the Schwarzschild objective lens focal length are given. In addition, tolerance and sensitivity analysis for the Schwarzschild objective lens, two spherical mirrors indicate that tilting the concave mirror (or secondary mirror) has a higher impact on the modulation transfer function values than tilts introduced by the convex mirror (or primary mirror). Finally, the performed tolerance and sensitivity analysis on the lens design suggests that decentering any of the mirrors by the same distance has the same effect on the modulation transfer function values.

Spectral characterization of postage stamp printing inks by means of Raman spectroscopy

A completely non-destructive analysis has been achieved using an ATR-FTIR spectrometer and the filtered laser beam, focalized by the Raman microscope objective lens.

Application of Micro-PIV on the Microscale Flow and a Modified System Based on Ordinary 2-D PIV

This paper briefly presents the working principle of micro-PIV (Particle Imaging Velocimetry) and its development and application on the microscale flow. Compared with ordinary PIV, micro-PIV has much higher spatial resolution. In addition, the adoption of fluorescent tracer and filter lens could enable flow field near wall surface to be measured. In view of the ordinary 2-D PIVs have been widespread among the scientific research institution related on fluid flow, the way that an ordinary 2-D PIV was modified to enable measurement of microscale flow was discussed in the paper. The extra elements of microscope objective lens, relay mirror, filter lens and telescopic focusing barrel are necessary. Some experiment results of the flow in microscale channels have been introduced to verify the availability of the modified PIV system. It could be found from the experimental results that the modified PIV system could be feasible and reliable for measuring micro-scale flows.

Alpha-Null Defocus: an Optimum Defocus Condition with Relevance for Focal-Series Reconstruction

Two optimum defocus conditions are well known to users of high-resolution transmission electron microscopes. Scherzer defocus is useful in high-resolution electron microscopy (HREM) because it produces an image of the specimen “projected potential” to the resolution of the microscope. Lichte defocus is useful in electron holography because it optimizes sampling in frequency-space by minimizing the slope of the microscope objective lens phase change out to the highest spatial frequency in the hologram, consequently minimizing dispersion. For focal-series reconstruction, the requirement to maximize transfer into the image of high-frequency diffracted beam amplitudes leads to a third optimum defocus condition.Image reconstruction methods allow the achievement of super-resolution - resolution beyond the native (Scherzer) resolution of the microscope - by correction of the phase changes introduced by the microscope objective lens. One such method is focal-series reconstruction, in which diffracted-beam information obtained at several different focus values is combined. to produce a valid super-resolution result, it is necessary to ensure that every spatial frequency is represented appropriately. Suitable choice of an optimum defocus produces optimum transfer of diffracted-beam amplitudes at any chosen spatial frequency.