Convergence adjusting method, signal generating apparatus, and projection display unit

1. Field of the Invention Where a stack projection operation is carried out using first and second projection display units, it is arranged such that the first projection display unit projects a crosshatch pattern continuously in time while on the other hand, the second projection display unit projects a pattern identical with that crosshatch pattern such that the pattern flashes at given intervals of time. Thereafter, the state of superposition between the patterns projected from the two projection display units is examined to carry out inter-set convergence adjustment between the display units.