Correction information calculator, image correction device, image display system, correction information calculation method

A correction information calculation method used in an image display system in which a plurality of projectors each including an image forming element collaboratively displays one image on a projection surface, the method comprising:

• calculating a first correspondence which is the correspondence between the coordinates of pixels on the image forming element and the coordinates of pixels on a first effective projection region of the projection surface;
• specifying a second effective projection region of the projection surface, different from the first effective projection region;
• and
• calculating correction information representing the correspondence between the coordinates of the pixels on the image forming element and the coordinates of the pixels on the second effective projection region based on the first correspondence and a second correspondence which is the correspondence between the coordinates of the pixels on the first effective projection region and the coordinates of the pixels on the second effective projection region.