How do ocular aids impact retinal risk when viewing divergent sources? We present ray tracing calculations for ocular aids used in several common configurations and compare risk relative to an unaided eye. Retinal irradiance values for sources of different subtence and divergence were calculated for ocular aids of different magnifying power. The data show the stark difference between point sources, like lasers, and extended sources, such as light emitting diodes ͑LEDs͒ and lamps. Arguing from fundamental physiological phenomena we compare the relative ocular risks of various sources under a range of viewing conditions and compare these calculations with standards proposed to classify such different sources. We conclude that, if point sources are correctly classified, then extended sources, such as LEDs, are overclassified by the IEC 825-1/CENELEC.

Although progress has been made in optical interconnections, electrical interconnections continue to dominate most of the hierarchical interconnect layers that comprise computer systems. (The delay in the industry's move to optics is largely due to the continued improvements in electrical links, most notably the addition of equalization schemes [1].) The challenges faced by electrical interconnections [2] are described along with a presentation of the potential benefits optical interconnections afford. Commercial success for optical interconnections has largely been in rack‐to‐rack links, where the distances are great enough to require the low loss advantages of optical transmission. Further work on optical schemes for each layer of interconnection hierarchy, rack to rack, board to board, and intraboard is presented. These schemes can be broken into two general types of guided wave solutions that use fibers or waveguides as transmission media and free‐space solutions, which require only the optical elements. Advantages and examples of links using each type are described. It is shown that free‐space optical interconnections board to board can reduce wiring congestion dramatically over electrical or guided wave approaches, which force all interconnections to pass between the boards through the backplane. The density achievable can be further improved by employing 3D interconnection arrangements which are discussed in the intraboard examples. Optical interconnection will gradually penetrate from the outer levels of the systems to the inner as the technology matures, but all of these interesting possibilities will remain possibilities unless future areas of study include focus on low cost, small size for high density and high reliability of optical interconnections and devices.

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