Method and means for automatically variably controlling display parameters

Claim 1

For use in controlling the Gray scale level of a video display and the display window of CT numbers in a computed tomography system, apparatus for automatically and variably generating a pulse train comprising manually operated pulse generation means for generating a first pulse train, means for receiving said pulse train and responsive to the frequency thereof for generating a second pulse train, the frequency of said second pulse train being nonlinearly proportional to the frequency of said first pulse train, said means for receiving including an oscillator and a plurality of frequency dividers connected with said oscillator for producing pulses at a plurality of pulse rates, and logic means for selecting a pulse rate depending on said frequency of said first pulse train, said logic means including a frequency to voltage converter connected to receive said first pulse train and generate a voltage in response thereto, a plurality of voltage comparators for receiving and comparing said voltage and a plurality of reference voltages and generating logic signals in response thereto, and logic gate means operably connected to receive said logic signals and in response thereto selecting a pulse rate.