An apparatus, method, and program for measuring the three-dimensional shape of an object by analyzing an optical pattern projected onto the object includes a line sensor and an image analysis unit. The line sensor reads the target object, onto which the optical pattern is projected. The image analysis unit analyzes the optical pattern in the image read by the line sensor based on a spatial fringe analysis method, and the image analysis unit computes the three-dimensional shape information on the target object. The phase of a pixel included in an image taken of the optical pattern is determined based on the brightness values of the pixel and at least one neighboring pixel in the image; thus the height information of the object can be determined. In addition, the height of the target object at a given position can be computed based on how much the phase of the optical pattern projected onto a certain position of the object is shifted from a reference phase.