a discontinuous portion detecting unit configured to detect discontinuous portions in pixel values of a plurality of pixels in image data in which light signals of the real world having continuity of the light signals of the real world in that, at any arbitrary position in a length-wise direction of an object in distribution of intensity of light from the object, the cross-sectional shape as the change in level corresponding to the change in position in the direction orthogonal to the length-wise direction are projected so that a part of the continuity of the light signals of the real world is lost;

a peak detector configured to detect the peak of change of the pixel values from the discontinuous portions;

a monotonous increase or decrease region detector configured to detect monotonous increase or decrease regions wherein the pixel values are increasing or decreasing monotonously from the peak;

a continuousness detector configured to detect, from the monotonous increase or decrease regions detected by the monotonous increase or decrease region detector, a monotonous increase or decrease region regarding which another monotonous increase or decrease region exists at an adjacent position on a screen, as a continuity region which is a pixel region having continuity of the image data in that a constant characteristic is obtained in a predetermined dimensional direction which is changed from the continuity of the light signals of the real world;

a direction detector configured to detect the direction of continuousness of the continuity region; and

an actual world estimating unit configured to estimate light signals of the real world by estimating the continuity of the light signals of the real world, based on the continuity region detected by the continuousness detector and the direction of the continuousness of the continuity region detected by the direction detector.