Abstract: The solid shape of an object is detected by viewing the objects along a Z-axis direction. A plurality of images of the object are picked up at different focus levels having correspondingly different Z-axis coordinate values. Focus measure values are calculated with respect to each of the pixels that are in each of the object images and that are designated by the same X- and Y-coordinate values. The focus measure values of the pixels in the object images having the same X- and Y-coordinate values are compared with each other to detect maximum focus measure values. The solid shape of the object is then estimated based on the Z-coordinate value of the focus level of the object image having the maximum detected focus measure values.