Regulating danger on the highways: hours of service regulations.

Objectives: Current hours of service regulations governing commercial truck drivers in place in the United States, Canada, Australia, and the European Union are summarized and compared to facilitate the assessment of the effectiveness of such provisions in preventing fatigue and drowsiness among truck drivers.

Methods: Current hours of service provisions governing commercial truck drivers were derived from governmental sources.

Results: The commercial truck driver hours of service provisions in the United States, Canada, and the European Union permit drivers to work 14 hours and those of Australia permit drivers to work 12 hours a day on a regular basis.

Chromatic confocal microscopy using staircase diffractive surface.

A chromatic confocal microscope (CCM) is a high-dynamic-range noncontact distance measurement sensor; it is based on a hyperchromatic lens. The vast majority of commercial CCMs use refractive-based chromatic dispersion to chromatically code the optical axis. This approach significantly limits the range of applications and performance of the CCM.

Coherence scanning interferometry: measurement and correction of three-dimensional transfer and point-spread characteristics.

When applied to the measurement of smooth surfaces, coherence scanning interferometry can be described by a three-dimensional linear filtering operation that is characterized either by the point-spread function in the space domain or equivalently by the transfer function (TF) in the spatial frequency domain. For an ideal, aberration-free instrument, these characteristics are defined uniquely by the numerical aperture of the objective lens and the bandwidth of the illumination source. In practice, however, physical imperfections such as those in lens aberrations, reference focus, and source alignment mean that the instrument performance is not ideal.