Abstract: A method of forming a minimum mean-square error linear filter photographically is disclosed.The optimum filter may be obtained photographically. In one form, a first photographic negative of a monolayer of cells having a high percentage of cells of the given type is made at the focal plane of a transforming lens mounted so as to collect the light scattered by the monolayer; and, developed for a gamma of unity. Thereafter, a second photographic negative is made at the same focal plane of a monolayer of cells containing a normal percentage of cells of the given type using the first negative as a filter. The second negative is developed for a gamma of two. The resulting photographic plate is a realization of the desired optimum (minimum mean-square error linear) filter.

Abstract: Method and apparatus for measuring the repetition rate of a series of electrical input pulses. An electrical quantity having a predetermined initial value changes at a predetermined rate in response to the presence of an input pulse; a later value of the quantity is detected in response to the presence of the next input pulse; and, in response to the later value of the quantity, an electrical output signal is provided that is indicative of the repetition rate of the input pulses. Typically the steps are repeated for a plurality of successive input pulses and a control signal maintains the detected later values of the quantity substantially equal to a predetermined comparison value. An alarm may be provided in response to any substantial change in the repetition rate of the input pulses.

Abstract: Cells of a given type spread among an ensemble of cells of various types are identified and, if desired, counted. Coherent light is directed toward a monolayer of cells of various types. The light scattered by the monolayer of cells is collected by a lens and the collected light is filtered by an optimum filter located in the focal plane of the lens. The optimum filter is a minimum mean-square error linear filter which suppresses light scattered by cells other than the given type of cell whereby the light scattered by the given type is enhanced. The intensity of the light passed by the optimum filter is related to the number of cells of the given type contained in the monolayer of cells. If desired, a second lens may be used to collect the filtered light and focus it toward an integrating and squaring detector.The optimum filter may be obtained photographically.