1. An image processing system comprising: a projection device for projecting a projected pattern to an observation target; an imaging device for capturing the projected pattern; and an image processing apparatus connected to the projection device and the imaging device, for performing shape reconstruction based on an input image including the projected pattern, the image processing apparatus including a personal computer configured to: fetch the input image captured by the imaging device and performing line detection for the projected pattern projected by the projection device, wherein the projected pattern is a grid pattern formed of wave lines, the wave lines are wavy curves having predetermined periodicity, the grid pattern formed of the wave lines is formed of a plurality of wave lines that are arranged at predetermined intervals, the grid pattern is a set of wave lines that intersect each other in two directions, and the interval of the wave lines in one of the directions is not equal to an integral multiple of a wavelength for the wave line in the other direction; and perform shape reconstruction by associating intersection points of vertical and horizontal lines extracted by the line detection with the projected pattern.