Double-pass Optical System Research Articles

Forward light scatter analysis of the eye in a spatially-resolved double-pass optical system

An optical analysis is developed to separate forward light scatter of the human eye from the conventional wavefront aberrations in a double pass optical system. To quantify the separate contributions made by these micro- and macro-aberrations, respectively, to the spot image blur in the Shark-Hartmann aberrometer, we develop a metric called radial variance for spot blur. We prove an additivity property for radial variance that allows us to distinguish between spot blurs from macro-aberrations and micro-aberrations. When the method is applied to tear break-up in the human eye, we find that micro-aberrations in the second pass accounts for about 87% of the double pass image blur in the Shack-Hartmann wavefront aberrometer under our experimental conditions.

Examination of the effect of furnace design on sensitivity in graphite furnace atomic absorption spectrometry

The performances of three small laboratory-made graphite furnaces, designed for use in electrothermal atomisation atomic absorption spectrometry (ETA-AAS) with a longitudinal magnetic-field Zeeman-effect background-correction system and operated without a sample drying stage, have been examined and compared with those of conventional tubular furnaces. The performance of a double-pass optical system was also examined. The purpose of this study was to obtain the lowest detection limit for copper with respect to the analyte concentration in the sample and also to minimise the cycle time per sample. The performances of the furnaces were related to a simple theoretical model of atomisation. It was found that the sensitivities of the commercial systems were an order of magnitude better than the laboratory-made furnaces but their minimum cycle times were twice as long, i.e., 1 min compared with 30 s. The use of a double-pass optical system led to a doubling of the sensitivity.

High efficiency symmetrical scanning optics

A compact, simple, polygon-type flying spot scanner with high light throughput, well controlled spot size and good linearity is described. This underfilled, double pass optical system with axial input provides a large scan angle with few optical elements and thus lends itself to a cost-effective design. It has been successfully implemented for several applications, including colour printing.

A Double Pass Spectrometer for the Far Infrared

A far ir spectrometer has been built which uses a double pass optical system to increase the spectral dispersion. Because of the energy limitations in this spectral range, this means of increasing the dispersion is an efficient way to improve the resolving power of a grating monochromator. The same optical system is also used to advantage in a lamellar grating interferometer where the increased dispersion improves the performance at higher frequencies. Consideration is also given to instrument errors and signal noise which can affect, and in some cases limit, the present performance of a far ir Fourier interferometer.