1. An apparatus for generating a depth signal for each of time-series images, the time series images including a first image and a second image, the apparatus comprising: a calculating unit configured to calculate a statistic value for pixel values of pixels for each of predefined areas in the first image, and calculate first evaluation values, respectively for predetermined base depth models, based on the calculated statistic value, wherein each of the predetermined base depth models has a depth structure pattern; a correcting unit configured to derive subsequent second evaluation values for the predetermined base depth models by correcting the first evaluation values for each of the predetermined base models, based on a set of second evaluation values previously derived for the second image and a first degree of similarity indicating a similarity between the predetermined base depth models; a selecting unit configured to select a base depth model for the first image having a highest second evaluation value for the first image, from the predetermined base depth models; and a generating unit configured to generate a depth signal based on the selected base depth model.