A novel superconducting single-photon detector ͑SSPD͒, intrinsically capable of high quantum efficiency ͑up to 20%͒ over a wide spectral range ͑ultraviolet to infrared͒, with low dark counts ͑Ͻ1 cps͒, and fast ͑Ͻ40 ps͒ timing resolution, is described. This SSPD has been used to perform timing measurements on complementary metal-oxide-semiconductor integrated circuits ͑ICs͒ by detecting the infrared light emission from switching transistors. Measurements performed from the backside of a 0.13 m geometry flip-chip IC are presented. Other potential applications for this detector are in telecommunications, quantum cryptography, biofluorescence, and chemical kinetics.
<p>ABSTRACT</p><p>PURPOSE: The optical quality of retinal images is dependent on the refracting elements of the eye including the nominally aspheric cornea and crystalline lens. This paper presents a retrospective theoretical analysis of the impact of corneal asphericity on the quality of retinal images. Clinical data are from the VISX Incorporated CustomVue IDE.</p><p>METHOD: Topography, contrast sensitivity, and visual acuity data were collected from 278 myopic eyes before and after wavefront-guided laser surgery. The measured corneal surface of each eye was fitted to a conic, and a Q-value was computed for a 5.5-mm pupil. A model eye was used to simulate various amounts of optical asphericity.</p><p>RESULTS: Preoperatively, most corneas exhibited negative conic shape constants. Postoperatively, corneas were about equally divided between positive and negative conies. There was no statistically significant correlation between the shape of the cornea and the subjects' perceptions of image quality including contrast sensitivity and visual acuity. Simulations showed that the corneal Q-value can vary from more to less prolate depending upon the shape of the internal surface.</p><p>CONCLUSION: Following wavefront-guided laser in situ keratomileusis (LASIK), contrast sensitivity is usually good and is not dependent upon the corneal conic shape. Better visual outcomes are more likely with a customized shape than a standard best conic shape. [J Refract Surg 2004;20:S581-S585]</p>
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