Minimum Aberrations Research Articles

Spectroscopic analysis of the sum-frequency response of the carbon-hydrogen stretching modes in collagen type I.

We studied the origin of the vibrational signatures in the sum-frequency generation (SFG) spectrum of fibrillar collagen type I in the carbon-hydrogen stretching regime. For this purpose, we developed an all-reflective, laser-scanning SFG microscope with minimum chromatic aberrations and excellent retention of the polarization state of the incident beams. We performed detailed SFG measurements of aligned collagen fibers obtained from rat tail tendon, enabling the characterization of the magnitude and polarization-orientation dependence of individual tensor elements Xijk2 of collagen's nonlinear susceptibility. Using the three-dimensional atomic positions derived from published crystallographic data of collagen type I, we simulated its Xijk2 elements for the methylene stretching vibration and compared the predicted response with the experimental results. Our analysis revealed that the carbon-hydrogen stretching range of the SFG spectrum is dominated by symmetric stretching modes of methylene bridge groups on the pyrrolidine rings of the proline and hydroxyproline residues, giving rise to a dominant peak near 2942cm-1 and a shoulder at 2917cm-1. Weak asymmetric stretches of the methylene bridge group of glycine are observed in the region near 2870cm-1, whereas asymmetric CH2-stretching modes on the pyrrolidine rings are found in the 2980 to 3030cm-1 range. These findings help predict the protein's nonlinear optical properties from its crystal structure, thus establishing a connection between the protein structure and SFG spectroscopic measurements.

Aberration analysis of decentered lenses for the compensation of vergence–accommodation conflict in virtual reality systems

Subject of study. This study considered optical virtual reality systems in which the use of decentered lenses was proposed to remove or reduce the vergence–accommodation conflict, which results in discomfort or quick fatigue of the user. Aim of study. The study aimed to investigate the possibility of using decentered lenses to compensate the vergence–accommodation conflict in virtual reality systems and to determine the optimal configuration of a two-component optical system. Methods. The required decentering values in the case of a shift of one or both components and aberration characteristics were analyzed. Main results. More exact equations for aberrations introduced into an optical system by decentered lenses upon a relatively large shift of lenses were obtained based on the relations of the third-order aberration theory. The minimum decentering and, consequently, minimum aberrations are obtained in the scheme when both components are decentered. An example of an optical system with decentered lenses designed considering the requirements on size and high image quality is presented. Practical significance. The obtained equations for the aberrations of decentered lenses enable the assessment of the effect of a transverse shift of lenses on image quality in virtual reality systems and can also be applied to analyze decentering aberrations in other schemes. The proposed designs of optical schemes can be utilized in virtual reality systems with reduced vergence–accommodation conflict.

Synthesis of Bifocal Mirror–Lens Cylindrical System with Minimum Aberrations

Synthesis of Bifocal Mirror–Lens Cylindrical System with Minimum Aberrations

Synthesis of Two-Mirror Bifocal Cylindrical System with Minimum Aberrations

Synthesis of Two-Mirror Bifocal Cylindrical System with Minimum Aberrations

An easy to construct sub-micron resolution imaging system

We report an easy to construct imaging system that can resolve particles separated by ge 0.68 upmu m with minimum aberrations. Its first photon collecting lens is placed at a distance of 31.6 mm giving wide optical access. The microscope has a Numerical Aperture (NA) of 0.33, which is able to collect signal over 0.36 sr. The diffraction limited objective and magnifier recollects 77% photons into the central disc of the image with a transverse spherical aberration of 0.05 mm and magnification upto 238. The system has a depth of field of 142 upmu m and a field of view of 56 upmu m which images a large ensemble of atoms. The imaging system gives a diffraction limited performance over visible to near-infrared wavelengths on optimization of the working distance and the distance between the objective and magnifier.

Eikonal Aberrations in Gradient Cylindrical Lenses

Approximate formulas are derived for eikonal on the output surface of a cylindrical dielectric lens with a gradient of refractive index along the Cartesian coordinate for a source that is displaced from the focal point on the symmetry axis of the lens. The first formula is obtained for the paraxial region and represents an expansion in powers of the longitudinal and transverse displacement of the source including terms of the first and second orders of smallness, and the second (integral) formula has no limitations on the numerical aperture. The first formula is used to obtain an equation of the focal curve. Errors of the formulas in the calculations of the eikonal and its aberrations on the output surface of the lens are analyzed. The second formula is used to find optimal parameters of the lens with parabolic variation in permittivity that provides minimum aberrations.

Method for compensation selection of a microlithographic optical system.

Computer-aided alignment is very important for the correction of aberrations due to construction imperfections of microlithographic optical systems. The compensation results mostly depend on the selection of compensators. In this paper, an effective method for compensation selection considering optomechanical constraints is presented. The techniques are based on the linearity of compensators and treat compensator selection as a combinatorial optimization problem with the objective of minimum residual aberrations and compensator adjustment ranges. The method is reliable and offers a better combination of compensators under constraints of optomechanical structure. As an example, the method was applied to a lithographic lens with a numerical aperture (NA) of 0.75. The results show that compensators with minimum objective function value would get minimum residual aberrations and adjustment ranges compared to those with larger objective function values. This method presented in this paper could be a good solution for compensation selection in lithographic lenses and other similar optical systems.

Initial configuration design method for off-axis reflective optical systems using nodal aberration theory and genetic algorithm

Initial configuration is important for optical system design, especially for systems with high requirements in specifications. The number and complexity of optical surfaces needed in an optical system largely depend on the choice of the initial configuration. It is essential to achieve a good initial configuration with minimum aberrations before using complicated surfaces. We propose an initial configuration design method for off-axis reflective optical systems. With this method, a good initial configuration with conic surfaces can be obtained directly. Nodal aberration theory and matrix method are used to calculate the aberration coefficients for the off-axis reflective optical system. Genetic algorithm is applied to search for the initial configuration with minimum aberrations. The validity of this design method is demonstrated by designing an off-axis three-mirror optical system.

On aberrations of eikonal in planar lens antennas

A formula for the eikonal distribution over the surface of a cylindrical dielectric lens with an error on the fourth-order of the displacement of the source from the focus is found. The accuracy of this formula and the first three terms of its expansion in this parameter for describing the eikonal and its aberrations are analyzed. A method for finding the parameters of the optical aplanatic lens (with minimum aberrations) is proposed. An approximate equation of the focal curve is derived.

Initial system design method for non-rotationally symmetric systems based on Gaussian brackets and Nodal aberration theory.

Freeform surfaces play important roles in improving the imaging performance of off-axis optical systems. However, for some systems with high requirements in specifications, the structure of the freeform surfaces could be very complicated and the number of freeform surfaces could be large. That brings challenges in fabrication and increases the cost. Therefore, to achieve a good initial system with minimum aberrations and reasonable structure before implementing freeform surfaces is essential for optical designers. The already existing initial system design methods are limited to certain types of systems. A universal tool or method to achieve a good initial system efficiently is very important. In this paper, based on the Nodal aberration theory and the system design method using Gaussian Brackets, the initial system design method is extended from rotationally symmetric systems to general non-rotationally symmetric systems. The design steps are introduced and on this basis, two off-axis three-mirror systems are pre-designed using spherical shape surfaces. The primary aberrations are minimized using the nonlinear least-squares solver. This work provides insight and guidance for initial system design of off-axis mirror systems.

Mapping optical path length and image enhancement using quantitative orientation-independent differential interference contrast microscopy.

We describe the principles of using orientation-independent differential interference contrast (OI-DIC) microscopy for mapping optical path length (OPL). Computation of the scalar two-dimensional OPL map is based on an experimentally received map of the OPL gradient vector field. Two methods of contrast enhancement for the OPL image, which reveal hardly visible structures and organelles, are presented. The results obtained can be used for reconstruction of a volume image. We have confirmed that a standard research grade light microscope equipped with the OI-DIC and 100 × / 1.3 NA objective lens, which was not specially selected for minimum wavefront and polarization aberrations, provides OPL noise level of ? 0.5 ?? nm and lateral resolution if ? 300 ?? nm at a wavelength of 546 nm. The new technology is the next step in the development of the DIC microscopy. It can replace standard DIC prisms on existing commercial microscope systems without modification. This will allow biological researchers that already have microscopy setups to expand the performance of their systems.

Passive focusing techniques for piezoelectric air-coupled ultrasonic transducers

This paper proposes a novel passive focusing system for Air-Coupled Ultrasonic (ACU) piezoelectric transducers which is inspired by the Newtonian–Cassegrain (NC) telescope concept. It consist of a primary spherical mirror with an output hole and a flat secondary mirror, normal to the propagation axis, that is the transducer surface itself. The device is modeled and acoustic field is calculated showing a collimated beam with a symmetrical focus. A prototype according to this design is built and tested with an ACU piezoelectric transducer with center frequency at 400kHz, high-sensitivity, wideband and 25mm diameter flat aperture. The acoustic field is measured and compared with calculations. The presented prototype exhibit a 1.5mm focus width and a collimated beam up to 15mm off the output hole. In addition, the performance of this novel design is compared, both theoretically and experimentally, with two techniques used before for electrostatic transducers: the Fresnel Zone Plate – FZP and the off-axis parabolic or spherical mirror.The proposed NC arrangement has a coaxial design, which eases the transducers positioning and use in many applications, and is less bulky than off-axis mirrors. Unlike in off-axis mirrors, it is now possible to use a spherical primary mirror with minimum aberrations. FZP provides a more compact solution and is easy to build, but presents some background noise due to interference of waves diffracted at out of focus regions. By contrast, off-axis parabolic mirrors provide a well defined focus and are free from background noise, although they are bulky and more difficult to build. Spherical mirrors are more easily built, but this yields a non symmetric beam and a poorly defined focus.

Monochrome HUD’s Imaging Projector Based on Laser-DMD System

Design and tolerance of a new head up display’s projector system is reported. It is based on laser-micro display modules. We designed optical diffraction limited modules and some of our novelties were compactness, using common material and spherical lenses in optical design, easy and economical manufacturing process, uniform intensity and minimum aberrations of final image, economical and repairable designed system. Projector magnification is 10.0X and diagonal of image plane is 76.2 mm. ZEMAX software is employed for optical design and tolerance.

Aberration design of zoom lens systems using thick lens modules.

A systematic approach for the aberration design of a zoom lens system using a thick lens module is presented. Each component is treated as a thick lens module at the beginning of the design. A thick lens module refers to a thick lens component with a real lens structure, like lens materials, lens curvatures, lens thicknesses, and lens interval distances. All nine third-order aberrations of a thick lens component are considered during the design. The relationship of component aberrations in different zoom positions can be approximated from the aberration shift. After minimizing the aberrations of the zoom lens system, the nine third-order aberrations of every lens component can be determined. Then the thick lens structure of every lens component can be determined after optimization according to their first-order properties and third-order aberration targets. After a third optimization for minimum practical third-order aberrations of a zoom lens system, the aberration design using the thick lens module is complete, which provides a practical zoom lens system with thick lens structures. A double-sided telecentric zoom lens system is designed using the thick lens module in this paper, which shows that this method is practical for zoom lens design.

Achromatic miniature lens system for coherent Raman scattering microscopy

We discuss the design and performance of a miniature objective lens optimized for coherent Raman scattering microscopy. The packaged lens assembly has a numerical aperture of 0.51 in water and an outer diameter of 8 mm. The lens system exhibits minimum chromatic aberrations, and produces coherent Raman scattering images with sub-micrometer lateral resolution (0.648 μm) using near-infrared excitation pulses. We demonstrate that despite the small dimensions of the miniature objective, the performance of this lens system is comparable to standard microscope objective lenses, offering opportunities for miniaturizing coherent Raman scattering imaging probes without sacrificing the image quality.

Non-approximate method for designing annular field of two-mirror concentric system

Annular field aberrations of a three-reflection concentric system, which are composed of two spherical mirrors, are analyzed. An annular field with a high level of aberration correction exists near the position where the principal ray is perpendicular to the object-image plane. Aberrations are determined by the object height and aperture angle. In this letter, the general expression of the system aberration is derived using the geometric method, and the non-approximate design method is proposed to calculate the radii of the annular fields that have minimum aberrations under different aperture angles. The closer to 0.5 (the ratio of the radius of convex mirror to the radius of concave mirror) is, the smaller the system aberration is. The examples analyzed by LABVIEW indicate that the annular field designed by the proposed method has the smallest aberration in a given system.

Layout of a double grid monochromator with minimum aberrations

This paper proposes a layout for a double grid monochromator with addition of dispersions, in which the aberrations of the objectives and of the dispersive elements (flat reflective diffraction gratings) are simultaneously minimized. Because of quadruple diffraction of the light beams, the layout can be fairly compact, with high angular dispersion and light-gathering power.

Electron Microscopy Enters a New Era Using Aberration Correction

Abstract Once in a while we have the privilege of participating in an activity that promises to radically improve our technical capability to explore materials at the microscopic level. The recent practical demonstration of aberration correction in the SEM, the TEM and the STEM signify nothing less than a revolution in the way that we design and operate electron optics for microscopy. Scherzer understood from the beginning of electron microscopy that an open magnetic lens having cylindrical symmetry will have positive, non-zero aberration coefficients, and so therefore will always have some minimum aberrations. In practical instruments, it was arranged that the limiting defect would be spherical aberration in the objective lens. This allowed the imaging performance to be largely characterized by a single parameter, spherical aberration, and also allowed a certain amount of image simulation and post-experiment analysis to facilitate interpretation of imaging results.

Chemical imaging sensor and laser beacon.

Design and functional aspects of PANSPEC, a panoramic-imaging chemical vapor sensor (PANSPEC is an abbreviation for infrared panoramic-viewing spectroradiometer), were advanced and its optical system reoptimized accordingly. The PANSPEC model unites camera and fused solid-state interferometer and photopolarimeter subsystems. The camera is an eye of the open atmosphere that collects, collimates, and images ambient infrared radiance from a panoramic field of view (FOV). The passive interferometer rapidly measures an infrared-absorbing (or infrared-emitting) chemical cloud traversing the FOV by means of molecular vibrational spectroscopy. The active photopolarimeter system provides a laser beam beacon. This beam carries identification (feature spectra measured by the interferometer) and heading (detector pixels disclosing these feature spectra) information on the hazardous cloud through a binary encryption of Mueller matrix elements. Interferometer and photopolarimeter share a common configuration of photoelastic modulation optics. PANSPEC was optimized for minimum aberrations and maximum resolution of image. The optimized design was evaluated for tolerances in the shaping and mounting of the optical system, stray light, and ghost images at the focal plane given a modulation transfer function metric.

PREVAIL: Operation of the electron optics proof-of-concept system

A proof-of-concept (POC) system was built to prove the electron optics concept of PREVAIL as a viable technology for next generation lithography (NGL), and is described elsewhere (H. C. Pfeiffer et al., J. Vac. Sci. Technology B, these proceedings; W. Stickel et al. ibid., these proceedings). The primary objective of the PREVAIL POC system is the embodiment of the curvilinear variable-axis lens (CVAL) optics which provides superior performance in terms of minimum geometric aberrations over unusually large deflection distances off the system axis (see Stickel et al.). Another major benefit of the CVAL is the minimization of the Coulomb interaction blur, since this approach permits the reduction of the column length to the smallest practical dimensions. The implementation of the PREVAIL CVAL requires a much higher degree of complexity than that of probe-forming systems, even of those which incorporate variable-axis immersion lenses [M. A. Sturans et al., J. Vac. Sci. Technol. B 8, 1682 (1990)] in the projection optics. The procedure used to establish the proper curvilinear variable-axis trajectory has required the development of hardware and software tools and is semiautomated. In this article we describe the means employed to properly establish the imaging conditions and the curvilinear trajectory of the deflected beam. Proper adjustment of the components is verified by comparison with the theoretically predicted excitation values for the deflection and axis-shifting yokes. Performance results presented by Pfeiffer et al. in terms of image blur and subfield distortion provide the proof of concept for the CVAL imaging conditions.