Static Aberrations Research Articles

Imaging performance of the liquid-crystal-adaptive lens with conductive ladder meshing

The liquid-crystal-adaptive lens (LCAL) is an electro-optical device that utilizes a graded index of refraction to bring light to focus. A set of electrodes controls the index variation in a liquid-crystal thin film. One can vary the focal length of the LCAL by changing the voltages applied to the device. The discrete nature of the electrodes causes phase aberrations. We introduce a novel electrode architecture, called conductive ladder meshing (CLM), that we developed to greatly reduce the static phase aberration (caused by the electrode structure). To reduce the dynamic phase aberration (associated with inaccurate voltages), we used a simulated-annealing voltage-dithering technique. The coherent transfer function of the LCAL was derived so that the performance of the CLM LCAL could be predicted theoretically. Theoretical analysis indicates that the CLM LCAL scatters less than 30% of incident light compared with scattering of 65% in the previous version. The focal-spot performance of the spherical LCAL was measured under coherent illumination for plane-wave illumination. Because of the improved quality of the spherical LCAL, true imaging experiments are demonstrated for a single incoming polarization under white-light illumination. Images formed by the spherical LCAL are comparable with those formed by a fixed lens in terms of resolution, although the contrast is worse.

Unified mechanical aberration theory of electrostatic focusing‐deflection systems

AbstractAn axially symmetric electrostatic focusing‐deflection system is indispensable in forming a focused ion beam. This paper describes a general procedure for quantitatively evaluating the effect of the mechanical error existing in the electrode of the electrostatic optical system on the optical characteristics. From the perturbation theory, a rigorous formula is derived for evaluating the aberrations up to the third order due to the mechanical errors. It is shown that the well‐known static deflection trajectory appears in the first‐order trajectory component. It is shown that the higher‐order trajectories (aberrations) can be represented by five aberration coefficients for the second‐order components and by 28 for the third‐order components.The present method can analyze the effect due to mutual interactions in the case where mechanical errors exist both in the deflection system and the focusing system which has been neglected. Further, in the derived evaluation formula, static mechanical aberration correction systems such as aligners and stigmators are taken into consideration. Hence, the method can evaluate the situation after the main mechanical aberrations are removed by correcting devices.

Superresolving phase conjugate scanning microscope

Analytical and experimental results of a new type of optical scanning microscope, which uses a phase conjugate mirror and pinholes to achieve superresolution, are presented. The phase conjugate scanning microscope has a higher Rayleigh resolution limit and better sectioning discrimination than conventional, single pass, and double pass scanning microscopes. It also can reduce the effect of static and dynamic aberrations on the imaging process, is very easy to align, and has the potential of introducing optical power gain into the system.