A method (100) of demodulating a real two-dimensional pattern (110) is disclosed. The method (100) estimates (120, 130) a quadrature two-dimensional pattern from the real two-dimensional pattern (110) using a smooth phase only transform having an anti-symmetric phase, such as a spiral phase filter (140). A demodulated image is created by combining (180) the real two-dimensional pattern (110) and the estimated quadrature two-dimensional pattern.