Abstract:
A discrimination reference level generator which provides a dynamically adjustable reference level for discriminating between the white background of a document and black characters imprinted on the document. The maximum contrast signal from document areas on either side of the document area being scanned are used to control the black-white discrimination level of the scanned area. Furthermore, correlation between the discrimination reference levels of adjacent document areas prevents a sudden decrease in the discrimination reference level between two adjacent document areas. The discrimination reference level is not permitted to fall below a predetermined minimum level which is constant for normal contrast but which is automatically raised when there is an extremely high contrast between the document and the characters imprinted thereon.
Abstract:
An analog-to-digital converter that eliminates dynamic coupling errors in a system where the measured signal and the reference signal are subject to such variations. This device sequentially samples an analog unknown voltage and a reference voltage and converts the sampled signals into digital information representative of the unknown voltage. Sampling and conversion is achieved in a three step process which alternates the reference and unknown signal inputs to an integrator and level holding circuits. The integrator output controls the duration of a digital counter which runs until the integrator output crosses a zero value. The result in the digital counter provides the binary value representative of the analog unknown signal. Dynamic coupling errors which occur during the reference and unknown signal sample times are eliminated by dividing the sample time of the unknown signal in two segments, a first sampling segment prior to sampling the reference signal, and a second sampling segment after the reference signal.
Abstract:
A control system for a stepping motor operating on the bang-bang principle in which opposing torque is exerted on the rotor of the motor as the rotor oscillates across its desired or home position. The degree of rotation of the rotor is indicated by a digital encoder, and associated circuitry or microprogramming provides a return torque on the rotor for a predetermined time, such as 120 microseconds, if the rotor oscillates across and beyond its desired position less than that amount required to produce an output pulse of the encoder. If the degree of oscillation is greater so that one but not two encoder pulses is produced, return torque is maintained until an encoder pulse is received after the rotor has reversed direction, and then no torque is applied on the rotor. If the oscillation is greater than that required to produce two encoder pulses but less than three encoder pulses, reverse torque is maintained on the rotor until the rotor returns to a rotative position corresponding to one encoder pulse. Then a torque is applied onto the rotor in the same direction as that in which the rotor initially rotated limited however to 120 microseconds duration. There is an overlap of torques between the two and one encoder pulse positions of the rotor as it returns to its home position. For oscillations of the rotor greater than those mentioned, similar applications of torque are made, so that the rotor is eventually brought to its home position.
Abstract:
A disk file having on one side of a disk a servo track and a plurality of data tracks all equally spaced on centers and a carriage translatable across the disk and having an array of read/write heads some of which are spaced on centers for the distance equal to the spacing between adjacent ones of said tracks and others of which are spaced on centers for multiples of the distance between adjacent ones of said tracks, the spacing between heads being such that when said heads are successively in alignment with said servo track the others of said heads are aligned with said data tracks.