Method and apparatus for obtaining distance data from an object to a lens by obtaining an image of the object by an image input unit for forming an image of the object through the lens on an image receiving plane. Two observed images Is and Is' with different blurs from the image input unit are obtained by making a position of the lens and/or a position of the image receiving plane with regard to the object different by a minute distance .DELTA.z. A filtering process is then performed by applying a filter to the two input observed images Is and Is', thereby providing two output images Fs and Fs'. The distance a up to the object is calculated by using the two output images Fs and Fs' obtained by the filtering process based on the relation between the two output images Fs and Fs' and radius s of the blur and the distance a from the lens to the object.