An electronic home plate provides assistance to an umpire in determining whether a pitch results in a "strike" or a "ball." The home plate is implemented with LEDs producing discrete pulses of infrared light beams extending vertically. As a moving ball intersects the pulses, light from the pulses is scattered and incident on photodetectors embedded in the home plate, producing a series of data points. Two stages of light compensation compensate the data points for ambient light, first by applying an offset current to a photodetector through a PNP transistor, and second by subtracting a measurement immediately before a pulse from a measurement during the pulse. A processor then fits the data points to a curve, to compute vertical and lateral positions of the ball, thereby determining whether the pitch passed within a strike zone. Other applications may similarly analyze the trajectory of other projectiles for various purposes.
