Optical System for Measuring Position in Space

There exist certain distinct advantages in accuracy and economy in the use of systems to measure vehicle position which operate at optical wavelengths. The positions measured are usually of critical importance to the success of a space mission. There are several types of navigational and tracking systems which produce data in an immediately usable form. Such real time systems, however, sacrifice some relative accuracy to gain speed of data availability. Stellar metric camera systems presently offer the most accurate means of determining position in space; however, there is an unavoidable time delay in reducing the data to a usable form. There is room for significant improvement in the errors of presently used stellar metric cameras, particularly in the geometrical optical characteristics of the lenses in both design and fabrication. The usefulness of such cameras can be extended by daylight use with the proper designs and techniques. Lunar-based cameras should also offer several advantages over Earth-based systems, but only at a high price. Recent developments in optical design techniques using high speed digital computers have brought fcjr greater sophistication and economy than had previously been possible. Vastly improved new optical designs are just waiting to be executed for application to the problems\u27of Measuring Positions in Space

Design and monitoring of narrow bandpass filters composed of non-quarter-wave thicknesses

Narrow bandpass filters have historically been designs of quarter waves at the passband wavelength, and have been monitored at the turning points using the passband wavelength. By direct monitoring at the passband wavelength, errors have been shown to be primarily self compensated, and have allowed much better performance than could otherwise be expected. The turning points are difficult to detect precisely and accurately because the change in transmittance with thickness becomes zero at the desired termination point. By proper design with non-quarter-wave layers, essentially the same spectral performance can be achieved by layer terminations that are far enough from turning points to be significantly more sensitive termination points. The design approach is to maintain the optical thickness of the reflector layer pairs at one half-wave of the passband wavelength, but change the ratio of the optical thicknesses of the high and low index layers. These can be adjusted enough so that the thicker layers contain two turning points and the last turning point in the layer can be more accurately and precisely determined. The error compensation benefit from the historic method should be maintained. This leads to potentially improved control during deposition and monitoring of narrow bandpass filters

Witness sample preparation for measuring antireflection

coating

Simulation comparisons of monitoring strategies in narrow bandpass filters and

antireflection coating

Limitations on Wide Passbands in Short Wavelength Pass Edge Filters

There are differences in the behavior of wide passband edge filters with short wavelength passbands and of those with long wavelength passbands. The bandwidth of the pass band is here defined by the longest wavelength in the band divided by the shortest wavelength. This is virtually unlimited in the case of a long wave pass filter. However, it is significantly limited in the case of the usual approach of using quarter wavelength layer thickness stacks for short wave pass filters. This limitation is encountered because the third and higher harmonics of the blocking band appear at the short wavelength position where the quarter wave optical thicknesses of the layers for the blocking band stack of layers become three (3) quarter waves, 5, 7, 9, etc., at the wavelength of that harmonic. It appears that bandwidths of over 2 start to have increasingly higher reflection losses, and bandwidths of 2.5 become virtually impractical for QWOT stacks. When band-passes broader than about 2 are needed for edge filters with a short wave passband, recourse to rugate-like designs is needed. Such designs can be achieved with only two homogeneous materials by employing the concept of the Herpin approximation, although many layers may be required. The influence of the indices of refraction of the materials, number of layers, and design approach on the bandwidth, average reflectance in the passband, band edge steepness, blocking density, and “squareness ” at the transition from the pass to blocking band are discussed

Ways that designers and fabricators can help each other

We show that, when designers and fabricators understand each other's art, there are ways to combine their techniques to achieve the best results with the minimum difficulty. We share some problems that we have encountered, and sometimes caused ourselves, in hopes of helping the reader avoid the same pitfalls.

RNAseq analysis of bronchial epithelial cells to identify COPD-associated genes and SNPs

Abstract Background There is a need for more powerful methods to identify low-effect SNPs that contribute to hereditary COPD pathogenesis. We hypothesized that SNPs contributing to COPD risk through cis-regulatory effects are enriched in genes comprised by bronchial epithelial cell (BEC) expression patterns associated with COPD. Methods To test this hypothesis, normal BEC specimens were obtained by bronchoscopy from 60 subjects: 30 subjects with COPD defined by spirometry (FEV1/FVC < 0.7, FEV1% < 80%), and 30 non-COPD controls. Targeted next generation sequencing was used to measure total and allele-specific expression of 35 genes in genome maintenance (GM) genes pathways linked to COPD pathogenesis, including seven TP53 and CEBP transcription factor family members. Shrinkage linear discriminant analysis (SLDA) was used to identify COPD-classification models. COPD GWAS were queried for putative cis-regulatory SNPs in the targeted genes. Results On a network basis, TP53 and CEBP transcription factor pathway gene pair network connections, including key DNA repair gene ERCC5, were significantly different in COPD subjects (e.g., Wilcoxon rank sum test for closeness, p-value = 5.0E-11). ERCC5 SNP rs4150275 association with chronic bronchitis was identified in a set of Lung Health Study (LHS) COPD GWAS SNPs restricted to those in putative regulatory regions within the targeted genes, and this association was validated in the COPDgene non-hispanic white (NHW) GWAS. ERCC5 SNP rs4150275 is linked (D’ = 1) to ERCC5 SNP rs17655 which displayed differential allelic expression (DAE) in BEC and is an expression quantitative trait locus (eQTL) in lung tissue (p = 3.2E-7). SNPs in linkage (D’ = 1) with rs17655 were predicted to alter miRNA binding (rs873601). A classifier model that comprised gene features CAT, CEBPG, GPX1, KEAP1, TP73, and XPA had pooled 10-fold cross-validation receiver operator characteristic area under the curve of 75.4% (95% CI: 66.3%–89.3%). The prevalence of DAE was higher than expected (p = 0.0023) in the classifier genes. Conclusions GM genes comprised by COPD-associated BEC expression patterns were enriched for SNPs with cis-regulatory function, including a putative cis-rSNP in ERCC5 that was associated with COPD risk. These findings support additional total and allele-specific expression analysis of gene pathways with high prior likelihood for involvement in COPD pathogenesis.https://deepblue.lib.umich.edu/bitstream/2027.42/142723/1/12890_2018_Article_603.pd

Simulation comparisons of monitoring strategies in narrow bandpass filters and antireflection coatings

The objective of this study has been to compare and quantify the simulated effects of noise, index errors, and photometric level errors on different optical monitoring layer termination strategies. A computer program to simulate optical thin film monitoring has been written for this work. The termination methods studied are: quartz crystal monitoring, photometric level cut, two types of turning point termination, and percent change from the extrema of the last maximum and minimum in the optical monitoring curve (POEM). Two turning point termination concepts are described. A narrow bandpass filter and a 4-layer antireflection coating design have been simulated as examples

ABSTRACT REPRODUCIBILITY IN OPTICAL THIN FILM PROCESSING PART 1, THE VACUUM AND PUMPING

Variations in vacuum and pumping practices used in optical thin film coating processes can cause a lack of reproducibility and adhesion problems with the product if not properly handled. The quality of vacuum needed, mean free path effects, cross-over pressures, backstreaming, and checks for the “health ” of the vacuum system are discussed and practical recommendations are made