An image sensor (10,110,210,310,410) including: a light receiving plane, two straight rows of pixels (2,4,6) disposed at right angles to each other, wherein the two straight rows of pixels (2,4,6) are disposed on the light receiving plane, such that there are surrounding positions adjacent to each of the two straight rows of pixels (2,4,6) on both respective sides thereof at which no pixel is disposed; signal read means for reading a signal determined by the amount of light received from each pixel (2,4,6) in each of the two rows of pixels; and signal processing means; wherein the two straight rows of pixels (2,4,6) are adapted to capture fragmental images of regular fringes generated from light reflected from an irradiated body (14,66) as images of linear fringes which have bright parts (38,44) alternated with dark parts (36,42) in accordance with the amount of light received by each pixel (2,4,6) of the two straight rows of pixels, wherein the two straight rows of pixels (2,4,6) in use acquire images of linear fringes crossing almost at right angles in two directions among the fringes projected onto the light receiving plane; wherein the signal processing means is adapted to calculate the positions of a bright part (38,44) or a dark part (36,42) of the linear fringes and the density of the linear fringes from the read signal by the signal read means; and to determine a change in attitude of the irradiated body (14,66) in accordance with the images captured by the two straight rows of pixels, the change of the positions of the bright part (38,44) or the dark part (36,42), and the change of the densities of the linear fringes; wherein the signal processing means includes a connection processing portion for connecting bright parts (38,44) together or dark parts (36,42) together of the orthogonal linear fringes in the two directions in accordance with a change in position of the bright parts (38,44) or dark parts (36,42) before and after a given period, in order to estimate a flat fringe image. a light receiving plane, two straight rows of pixels (2,4,6) disposed at right angles to each other, wherein the two straight rows of pixels (2,4,6) are disposed on the light receiving plane, such that there are surrounding positions adjacent to each of the two straight rows of pixels (2,4,6) on both respective sides thereof at which no pixel is disposed; signal read means for reading a signal determined by the amount of light received from each pixel (2,4,6) in each of the two rows of pixels; and signal processing means; wherein the two straight rows of pixels (2,4,6) are adapted to capture fragmental images of regular fringes generated from light reflected from an irradiated body (14,66) as images of linear fringes which have bright parts (38,44) alternated with dark parts (36,42) in accordance with the amount of light received by each pixel (2,4,6) of the two straight rows of pixels, wherein the two straight rows of pixels (2,4,6) in use acquire images of linear fringes crossing almost at right angles in two directions among the fringes projected onto the light receiving plane; wherein the signal processing means is adapted to calculate the positions of a bright part (38,44) or a dark part (36,42) of the linear fringes and the density of the linear fringes from the read signal by the signal read means; and to determine a change in attitude of the irradiated body (14,66) in accordance with the images captured by the two straight rows of pixels, the change of the positions of the bright part (38,44) or the dark part (36,42), and the change of the densities of the linear fringes; wherein the signal processing means includes a connection processing portion for connecting bright parts (38,44) together or dark parts (36,42) together of the orthogonal linear fringes in the two directions in accordance with a change in position of the bright parts (38,44) or dark parts (36,42) before and after a given period, in order to estimate a flat fringe image.