Reduction Of Chromatic Aberration Research Articles

Design, Fabrication and Analysis of a Hybrid-Order Monolithic Imaging Diffractive Lens on a Germanium Substrate

Diffractive optical elements are gradually replacing some conventional optical elements and becoming a key component of optical systems due to their unique phase modulation function. However, the imaging performance will be reduced due to the fact that this single-sided microstructured lens still produces chromatic aberration. Therefore, the key issue for the application of diffractive optical elements in optical systems is the reduction of chromatic aberration, and diffractive lenses with double-sided microstructures are proposed as a solution. This research describes the design and analysis of a 70-mm-diameter, 296-mm-focal-length double-sided microstructured hybrid-order monolithic imaging diffractive lens operating in the mid-wave infrared region (3.7-4.7 μm). The design minimizes chromatic aberration by up to 30 times compared to a standard harmonic diffractive lens and improves the image performance of a single-lens optical system operating in the infrared range. Experiments indicate that this design is capable of achieving single-lens imaging with high sensitivity for optical systems with a measured NETD ≤ 50 mK. The analysis of the experiments yielded suggestions for future research.

Chicago aberration correction work

The author describes from his personal involvement the many improvements to electron microscopy Albert Crewe and his group brought by minimizing the effects of aberrations. The Butler gun was developed to minimize aperture aberrations in a field emission electron gun. In the 1960s, Crewe anticipated using a spherical aberration corrector based on Scherzer's design. Since the tolerances could not be met mechanically, a method of moving the center of the octopoles electrically was developed by adding lower order multipole fields. Because the corrector was located about 15 cm ahead of the objective lens, combination aberrations would arise with the objective lens. This fifth order aberration would then limit the aperture of the microscope. The transformation of the off axis aberration coefficients of a round lens was developed and a means to cancel anisotropic coma was developed. A new method of generating negative spherical aberration was invented using the combination aberrations of hexapoles. Extensions of this technique to higher order aberrations were developed. An electrostatic electron mirror was invented, which allows the cancellation of primary spherical aberration and first order chromatic aberration. A reduction of chromatic aberration by two orders of magnitude was demonstrated using such a system.

Yellow Intraocular Lenses – To Block or Not to Block

Yellow filters for the eye have been of interest to ophthalmologists and optometrists for the last 30 years. Certain fish species can change the colour of the cornea in response to the level of illumination and regulate the amount of short-wavelength light reaching the retina. A positive influence of yellow eye filters on reduction of chromatic aberration has been found in a fish eye model. Blue-light-filter (yellow) intraocular lenses (IOLs) were introduced for cataract surgery almost 20 years ago. The main advantage of yellow IOLs is thought to be the reduction of chromatic aberration under photopic conditions and protection of the retina from phototoxic short-wavelength light, especially in eyes at risk of age-related macular degeneration (AMD). This article highlights the importance of yellow IOLs for cataract surgery in terms of quality of vision and AMD protection.

Non-paraxial analysis of curved analogue lens with multiple-phase jump

The non-paraxial analysis of the analogue waveguide Fresnel lens with curved entrance diopter and multiple-phase jump is presented. The finite length of the element's pads is included into the design. The alteration of both the curvature and the multiplication factor allows us to reduce off-axis aberration and to overcome the photolithographic resolution limits which seriously affect the fabrication of conventional analogue lenses. In the modelling, a hybrid numerical procedure has been used, which is a combination of ray tracing inside the lens and Fresnel-Huygens integral behind the lens; this procedure has been shown to work reliably in the non-paraxial region. The curved analogue lens based on the assumption of infinitesimal pad's length and the plane analogue lens with multiple-phase jump are also discussed as special cases of the generalized structure. Finally, the possibility of chromatic aberration's reduction is examined.

Effect of a yellow ocular filter on chromatic aberration: the fish eye as an example.

Reduction of chromatic aberration is one of the suggested functions of yellow ocular filters. This possibility was tested by (1) determining the effect of an artificial yellow filter on the chromatic aberration of the eye of two fish species having no obvious ocular filters and (2) comparing in vivo chromatic aberration with that of the excised lens in a species of fish having a yellow cornea. The results indicate that yellow filters reduce the measured chromatic aberration of the eye by more than one-third.

Experimental Investigation of Chromatic Aberration in the Electron Microscope

Experimental results on the reduction of chromatic aberration in the magnetic electron microscope are described. It is proved that the chromatic field aberration can be completely compensated by a proper combination of two lenses with adequately designed pole pieces and the voltage stabilization tolerance is greatly improved. Micrographs with a resolution of about 5 mμ can be obtained even under a voltage fluctuation as large as ΔE/E=1.10−2.