Abstract: A power control system for the heat lamps for typically drying a continuous web of paper in order to provide a linear moisture profile locates the actuating thyristor type switch at each zone where the heater lamps themselves are located. Thus, computer control can be centralized and wiring minimized. The parameters of minimum flicker for unity power factor and high resolution power control are achieved by utilizing the timing signals provided by the zero crossings of the three-phase AC line voltage input and controlling either half cycles or partial half cycles for each zone. Computing time is reduced by providing for scratch pad memory tables which can rapidly be scanned or sequenced through by a zone pointer.

Abstract: A method for the automatic fine focusing of an image scanning densitometer, micrometer, or television camera or the like, after an initial manual focus has been made on the edge of a discernible feature on the surface of an object of interest. A plurality of at least three, and preferably five, scans are made across the image of the feature at a corresponding plurality of focus positions, and the variations in light intensities are noted at each of a plurality of locations in each scan so that an edge value may be determined for each focus position. If plotted, edge values as a function of focus position appears as a second order curve of the form, edge value=ae.sup.2 +be+c, from which the values of the coefficients "a" and "b" may be determined by the least squares best fit method. When the derivative of the curve equation is made equal to zero to correspond to a zero slope or bottom of the curve, the best focus position is readily determined to that the precise focus may be adjusted to that position.

Abstract: In making precision measurements with a television camera tube, the inherent scan non-linearity and magnification variations are readily calibrated by painting a grid of known dimensions on the tube face.