Abstract: A broadband light source with a sufficiently long coherence length is impinged on the optical cavity. The broadband laser light reflects from the first and second surfaces of the cavity. The two light beams, either reflected or transmitted, are phase shifted from one another by an amount proportional to the optical path length of the cavity and inversely proportional to the wavelength of the light (4?nd/?) The two light beams interfere with each other and form a modulated light beam that has a spectrum approximately like the laser's broadband spectrum multiplied by a cosine with a frequency 4?nd/?. The modulated light beam is coupled to a spectrometer that measures the intensity of the light as a function of wavelength over a range of wavelengths. The Fourier transform of the spectrum contains a peak that is related to the OPL and is located at 2*n*d where n*d is the OPL.

Abstract: A broadband light source with a sufficiently long coherence length is impinged on the optical cavity. The broadband laser light reflects from the first and second surfaces of the cavity. The two light beams, either reflected or transmitted, are phase shifted from one another by an amount proportional to the optical path length of the cavity and inversely proportional to the wavelength of the light (4?nd/?) The two light beams interfere with each other and form a modulated light beam that has a spectrum approximately like the laser's broadband spectrum multiplied by a cosine with a frequency 4?nd/?. The modulated light beam is coupled to a spectrometer that measures the intensity of the light as a function of wavelength over a range of wavelengths. The Fourier transform of the spectrum contains a peak that is related to the OPL and is located at 2*n*d where n*d is the OPL.

Abstract: A pair of freely rotatable rolls bear against the opposite edges of a moving web. Each roll is mounted with its axis generally coaxial with that of the other roll, parallel to the adjacent rollers of the web transport systems and perpendicular to the direction of web movement. A support arm for each roll is pivotally connected to a fixed support, with the pivotal axis generally parallel to that of the roll, so that the weight of the roll pivots the arms towards the vertical and causes the roll to bear against the upper surface of the web. A constant bias force may be applied to the pivotal support arm to decrease (or in some circumstances to increase) the force with which gravity causes the roll to bear against the web.

Abstract: A core chuck comprising radially movable exterior jaw members, means operative in response to a relative rotation between the jaw members and those means to apply a radially outward force to the jaw members, and biasing means for urging the jaw members toward a predetermined radial position. The biasing means comprise a band spring disposed in axially aligned recesses in surfaces of the jaw members, at least one of the recesses being provided with spring retainer means preventing removal of the spring from the recess in a radial direction.

Abstract: A chuck for internally gripping a hollow member comprising an interior member having a longitudinal axis and including a plurality of generally planar exterior surfaces each parallel to the axis; a plurality of rollers, each roller parallel to and in contact with one of those surfaces; a plurality of jaw members, each having an arcuate interior surface in contact with at least one of the rollers; and means for resiliently maintaining the jaw members in contact with the rollers.