Abstract: An optical oil monitor that measures particle contamination in oil by passing light through an oil sample and picking up the light that is scattered at 90.degree. by the particle contaminaton and measures chemical breakdown by the attenuation of the light passing substantially straight through the oil with a second sensor. Alternately a sample and a reference are passed between the light responsive sensors for error correction and calibration so that each sensor will have an output signal alternating between a sample signal and a reference signal. A control signal of the same frequency is provided in combination with a plurality of gates to separate the sample and reference signals. The attenuation reference signal is compared to a standard signal to produce an error output for regulating the intensity of the light source to compensate for power source fluctuations, lamp characteristic changes, window soiling and the like.

Abstract: An interferometer for analyzing electromagnetic frequency spectra including a movable mirror supported on two air bearings such that the center of support of the bearings continuously coincides with the center of gravity of the movable mirror during the motion of the mirror. The air bearings engage two parallel, spaced apart lateral rods that maintain the optical alignment of the mirror. To facilitate making spectral measurements, the interferometer also incorporates a laser for producing monochromatic light that is directed through a primary beam splitter to provide a periodic fringe pattern as the mirror moves and a white light directed through a secondary beam splitter to provide a reproducible reference point.

Abstract: An interferometric device is provided for measurement of the variations in length of a sample under the influence of temperature, the length of the sample being within a plane of reference and a plane of measurement defined by two plane terminal faces of the sample.