Abstract: In order to accurately measure time interval Tx from time t.sub.j to time t.sub.k, the pulse widths of a start interpolation pulse and a stop interpolation pulse must be measured accurately. The invention uses two time-to-voltage converters, one for the start interpolation pulse and the other for the stop interpolation pulse, to convert these pulses to corresponding voltage signals to thereby measure the pulse widths. These converters each comprises a high speed circuit which comprises a current switch, a capacitor, a constant current source and a diode. Advantageously, even though the start and stop interpolation pulses occur close to each other, the pulses can be measured accurately. Also, even though the pulses occur at short intervals, the time interval Tx can be measured accurately.

Abstract: A method and system for generation of a quadratic curve signal expressed by f(x, y)=0 nonparametrically on coordinates X, Y, wherein, when linear micro-coefficients in the directions x, y are points (x, y) are given as fx, fy, respectively, the signs of fx, fy are decided and fx, fy are compared for dimensions with each other, thereby limiting the point to be selected next, to two points; then the value of new f(x,y) obtainable through selecting each point, are calculated; absolute values of the new f(x, y) are compared, the point giving the smaller value being selected as the next point; and repeating the aforementioned procedure, thereby to generate a quadratic curve signal expressed by f(x, y)=0.