The integrated Stiles-Crawford function is commonly used as apodization model for vision through the natural eye pupil. However, this method does not account for possible effects related to the retinal thickness, the large length-to-diameter aspect ratio of the photoreceptors, or the use of nonMaxwellian illumination. Here, we introduce a geometrical optics model to calculate the fraction of overlap between light at the retina and the photoreceptor outer segments where absorption triggers vision. The model, which does not account for photoreceptor waveguiding, is discussed for both Maxwellian and nonMaxwellian illumination. The integrated Stiles-Crawford effect is analyzed experimentally with a uniaxial pupil-size flicker methodology and we find that the psychophysical measurements match better to the geometrical optics predictions than direct integration of a Stiles-Crawford function.
Interruptdriven digital controller for a magnetic suspension system Rev. Sci. Instrum. 60, 456 (1989);Single-axis magnetic suspensions, using optical position sensing and dc electromagnets, have been developed with eight-bit-word digital controllers that replace the familiar analog phase-advance or proportional-plus-derivative circuits. Control algorithms are obtained by a simple curve-fitting approach to signals sampled at constant rates. Stable suspension has been demonstrated at sampling rates down to 75Hz w hen the magnet current has series transistor regulation, and at 100 Hz in a thyristor-regulated system.
A split-beam position detector for single-axis magnetic suspension systems has been modified by including a narrow-angle prism to produce symmetrical deflection of the two beams. The modified system is relatively insensitive to positioning of the components, and has a wider range of linear response.
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