1. A method of performing convergence calibration for a display using multiple beams to generate a video display on a screen, comprising the steps of: (a) projecting a reference pattern onto a sensor having a plurality of sensing sections and expanding a first area of the reference pattern from a first side of the sensor; (b) measuring first image signals with the plurality of sensing sections of the sensor from the reference pattern while performing step (a); (c) outputting first image signals measured by each of the plurality of sensing sections of the sensor in step (b); (d) projecting a reference pattern onto the sensor and expanding a second area of the reference pattern from a second side of a sensor; (e) measuring second image signals with the plurality of sensing sections of the sensor from the reference pattern while performing step (d); (f) outputting second image signals measured by each of the plurality of sensing sections of the sensor in step (e); and (g) generating parameters of the display system based on the first and second image signals outputted in step (c) and (f) for adjusting images of the display.