1. A method for depth map quality enhancement of defective pixel depth data values in a three-dimensional image, the method comprising the steps of: a) determining depth measurement data relating to a scene; b) detecting defective pixels within the depth measurement data by determining and using, for each pixel, depth related directional derivatives in at least one direction; c) defining a depth correction for each detected defective pixel; and d) applying the depth correction to the depth measurement data of each detected defective pixel; characterised in that the defective pixels comprise interpolated pixel data values located at edges between a foreground object and a background object in the three-dimensional image, and wherein step b) further comprises using the depth related directional derivatives to identify defective depth measurements of pixels at edges when at least one depth directional derivative of a pixel is greater than a predetermined threshold and if at least two consecutive directional derivatives have same sign; and in that step c) comprises, for each identified defective pixel, the steps of: c1) determining a vector in relation to at least one of the depth directional derivatives; c2) determining the normal to the determined vector; c3) determining a weighting factor parameter using at least one of the determined vector and the normal to the determined vector; and c4) determining a correction factor using at least one of the weighting factor parameter and the information relating to neighbouring pixels.