A method of obtaining on-line data useful in determining the center of area or centroid of a geometrical area of unspecified shape lying in a larger x-y scan field and having its existence indicated by a level discriminated amplitude or intensity or a parameter measurable in the z-dimension comprising; scanning the x-y field in a known raster pattern and obtaining a series of discrete output voltage pulses related to elemental x-y points in the scan field and having an amplitude related to the amplitude or intensity of the said parameter; generating a series of discrete clock pulses related to elemental x-y points in the scan field; obtaining a series of x and y synchronizing pulses from and related to the x-y scan field; establishing in relation to the clock pulses and the x and y synchronizing pulses a smaller x-y scan field in the form of a rectangular window around the geometrical area in the larger x-y scan field, the boundaries as x-y co-ordinates of the said window being known; identifying, from the series of discrete clock pulses, those pulses that coincide with pulses obtained above having an amplitude above a preset voltage level and which fall within the boundaries of the smaller x-y scan field such as to define sample point areas in the geometrical area; making an overall count of the number of pulses identified above, making a count of the number of elemental x-y point each of the pulses identified above are spaced from a boundary of the window in both the x and the y directions to provide x-moment arm counts and y-moment arm counts, and summing the x-moment arm counts and the y-moment arm counts, said counts taken with the count obtained from above providing data for computing the center of area or other mathematical functions of the geometrical area.

The field observed by a video camera includes a desired target which is to be encompassed by an electronic window. The acquisition of the target is controlled initially by a light pen to position the electronic window on the target displayed on the screen of a receiver. Automatic video tracking proceeds then by measuring the mean video level in the vicinity of the target, adjusting the signal to this level and rectifying it, and then periodically measuring the difference in energy in the two successive halves of the window along the axis in question, this measurement giving the positional divergence between the center of the window and the energy center of the target. Corresponding error signals are used to move the window to keep the target centered therein.

A method for distributing clocks to flip-flop circuits which constitute a logic circuit includes obtaining a timing slack of a first minimum delay time with respect to a minimum delay constraint time and a timing slack of a first maximum delay time with respect to a maximum delay constraint time for a clock in an input path to a flip-flop circuit, obtaining a timing slack of a second minimum delay time with respect to a minimum delay constraint time and a timing slack of a second maximum delay time with respect to a maximum delay constraint time for a clock in an output path from all the flip-flop circuits which receive the clocks from a clock terminal directly and obtaining a delay value which maximizes a minimum value of each of the first and second minimum delay time and maximum delay time of timing slacks.