In a state in which a reference light source emits light, display elements of a display device are caused to light up in each of lighting patterns for causing any adjacent display elements not to light up simultaneously. A captured image acquirer acquires image data about an image captured in each of the lighting patterns, a display element position calculator determines the position of each of the display elements and the position of the reference light source on each of the images, a display element brightness calculator calculates brightnesses from the pixel values at the determined positions, a relative brightness calculator calculates a relative brightness of each of the display elements with respect to the brightness of the reference light source, and a display element output coefficient calculator calculates coefficients for making the brightnesses of the display elements uniform.