The talbot effect : Fresnel diffraction of amplitude and phase gratings

Ph.D.Donald C. O'She

Broadband Variable Transmission Sphere for Fizeau Interferometry

Transmission spheres used in interferometry are specified by f-number and source wavelength. In this paper, we explore a broadband variable transmission sphere (BVTS) system based on freeform Alvarez lenses that enables variable operation across a broad range of f-numbers and wavelengths. Potential applications and performance tradeoffs are discussed in comparison to conventional spherical transmission spheres. Simulation results are presented for f/15 to f/80 configurations from visible to long-wave infrared sources in a Fizeau interferometer. Simulation results highlight that spherical, coma, and astigmatism impose limits on surface measurement quality

Fabrication Of Micro Optics On Coreless Fiber Segments

Fabrication of micro optics for fiber optics applications is a challenge due to their size and the issues associated with alignment of the optics to single-mode fibers. This study summarizes a method for fabricating diffractive optical elements on the ends of coreless fiber segments for passive alignment to single-mode fibers. Results are presented for passively aligned diffractive lens elements used for both collimation and beam shaping. © 2003 Optical Society of America

Predictive models for the Strehl ratio of diamond-machined optics

International audienceThis paper provides a practical connection between the Strehl ratio as an optical performance metric and manufacturing parameters for diamond machined optics. The choice of fabrication parameters impacts residual mid-spatial frequency groove structures over the part's surface, which reduce optical performance. Connections between the Strehl ratio and the fabrication parameters are studied using rigorous Rayleigh-Sommerfeld simulations for a sample optical system. The connections are generalized by incorporating the shape of diamond-machined groove structures and the effects of optical path differences for both transmissive and reflective optics. This work validates the analytical representation of the Strehl ratio as a Fourier transform of a probability density that relates to surface errors. The result is a practical tool that can be used to guide the choice of machining parameters to achieve a targeted optical performance

Between Copper, Silver and Gold: Japanese Banks of Issue in Taiwan, Northeast China and Korea, 1879–1937

This article provides the first comparative overview in English of Japanese colonial banks before World War II with an emphasis on their roles as banks of issue in Taiwan, Korea and Northeast China. It discusses at length similarities and differences in these banks’ note circulation patterns, in their note-reserve requirements and their actual application, and in their geographical spread and respective colonial mandates. There was some variation in Japanese bank note issuance in the colonial setting of Korea and Taiwan, in ‘Manchukuo’ and in those parts of China that remained nominally sovereign. But all Japanese colonial banks seem, in one way or another, to have astutely adjusted the spread of their note issue in order to control for flagging demand due to nationalist boycotts, or to conversely cash in on demand spurts for notes resulting from crises in the indigenous financial sector. The banks of issue under review here were theoretically subject to a 100 per cent reserve requirement, but the make-up of their metallic bullion reserve and the degree of their notes’ convertibility were very dissimi¬lar, reflecting varying local conditions. Both in terms of reserve ratios, and note denominations—the banks prudently followed charter obligations that were devised by the Japanese Treasury but, at the same time, were reminiscent of the obligations that British overseas banks also had to abide by. Thus, the findings discussed here shed light on the inception and adaptability of Japanese colonial policy in the lead-up to the Pacific War