Optical systems are often athermalized over large temperature ranges through the proper choice of glasses and mounting materials. However, variations in the coefficients of thermal expansion (CTE) and thermo-optical coefficients that govern thermal behavior are seldom included in the tolerance analysis. Manufacturers rarely provide these material tolerances and we can only account for their effects through custom macros in lens design software. We demonstrate that a first-order sensitivity analysis on the change in focus position at each environmental condition accurately predicts the degradation of the system performance. We verified this correlation by creating a custom catalog of identical glasses with perturbed thermal parameters and evaluating the RMS wavefront error for each material substitution.
In the design of optical assemblies, emphasis is placed on tolerancing the surface irregularity, which is a driving factor in price and manufacturing prices and time during polishing. Quite often, the default irregularity tolerance in modeling software is assumed to be a 50:50 split between astigmatism and 3rd order spherical aberration (i.e. symmetric zonal errors). In this paper, we reviewed the irregularity of over 1,000 custom fabrication optical surfaces. We looked at the relationship between the spherical and astigmatism aberrations and found generally that a surface will be either astigmatic or spherical, but rarely a mixture of the two. We also looked at the PV and rms of the surfaces and how that compares to the model and the general knowledge. One striking result of our analysis came from a closer analysis of how the optical modeling software package handles ‘power’ errors in the irregularity tolerance. It is possible that there is a mismatch between the model and the optical manufacturer.
By utilizing the Hydrogen-Lyman-α (HLA) source at 121.6 nm, we hope to achieve an intrinsic resolution of 247 nm at 0.3 numerical aperture (NA) and 92 nm at 0.8 NA. The motivation for 121.6 nm microscopy is the existence of a transparent window in the air absorption spectrum at that wavelength, which allows for the sample to be in air while the microscope is in an enclosed nitrogen environment. The microscope objective consists of two reflective optics and a LiF window, and it has been designed to demonstrate diffraction limited performance over a 160μm full field at 121.6 nm. The optomechanical design consists of mechanical subcells for each optical component, precision spacers and a barrel bore, which allow for submicron control of tolerance parameters.
Nano-scale resolution in miniature optical systems has been realized in the optical data storage industry. Numerical
apertures greater than unity have been achieved in by utilizing the high index material of a hemispherical Solid
Immersion Lens (SIL), which increases the resolution of the backing objective by a factor that is related to the refractive
index of the SIL. In this research, a custom Hyper-Blu-Disc (HBD) NA=1.4 SIL objective is utilized for high-fidelity
readout of data pits beneath a 100μm thick cover layer on an optical Blu-Ray Disc. If realized commercially, the increase
in data density could be 3X today’s Blu-Ray technology. A distinct difference between this work and other work with
SILs in optical data storage is the relatively thick cover layer of 100μm. Recently, there has been interest in discovering
new ways to apply the technology and methods used in optical data storage for other means. The inherent design of the
HBD objective to image through a shallow layer of dielectric material may lend itself to be used as an effective means
for characterizing subsurface damage in optical materials. This research will furthermore investigate the HBD objective
as a means of detecting subsurface damage.
We show the design for a laser scanning microscopy defect detection system based upon the idea that the light can reflect off a photoresist-laden fused-silica sample containing defects, allowing height and depth information to be obtained through changes in light intensity. Image registration using predefined points is employed. Image processing techniques involving median and deconvolution filtering are used. Results show that the 2.1-μm resolution of these defects is obtainable, and receiver operating characteristic curves are used for quantifying results. Discriminabilities of 0.73 are achieved. Preliminary results for larger-array patterns through stitching processes are also shown.
Coatings of various metalized patterns are used for heating and electromagnetic interference (EMI) shielding
applications. Previous work has focused on macro differences between different types of grids, and has shown good
correlation between measurements and analyses of grid diffraction. To advance this work, we have utilized the
University of Arizona's OptiScan software, which has been optimized for this application by using the Babinet Principle.
When operating on an appropriate computer system, this algorithm produces results hundreds of times faster than
standard Fourier-based methods, and allows realistic cases to be modeled for the first time. By using previously
published derivations by Exotic Electro-Optics, we compare diffraction performance of repeating and randomized grid
patterns with equivalent sheet resistance using numerical performance metrics. Grid patterns of each type are printed on
optical substrates and measured energy is compared against modeled energy.