Patent ID: 8873175

Claim:
An optical structure having two surfaces that are different in arrangement on both sides, and being made of an optical medium that is light transmissive, the optical medium having a refractive index n of more than √(4+2√2), one of the two surfaces of the optical structure being entirely formed by combining one or more 45° inclined planes each of which is a flat surface whose normal line is orthogonal to one of principal axes x, y, and z of a rectangular coordinate system and is located at an angle of 45° with respect to each of the other two of the principal axes, the other of the two surfaces being entirely formed by combining one or more principal axis planes each of which is a flat surface whose normal line is in parallel with any one of the principal axes x, y, and z of the rectangular coordinate system, and the one and the other of the two surfaces not overlapping each other, in a case where light beams having entered the one or more 45° inclined planes from an outside of the optical medium at any entrance angle enters the one or more principal axis planes either directly or after having experienced multiple internal reflection, the light beams being brought into contact with the one or more principal axis planes at an angle equal to or larger than a critical angle of total internal reflection without fail, and being prevented from being transmitted through the one or more principal axis planes by being totally reflected by the one or more principal axis planes, and in a case where light beams having entered the one or more principal axis planes from the outside of the optical medium at any entrance angle enters the one or more 45° inclined planes either directly or after having experienced multiple internal reflection, the light beams being brought into contact with the one or more 45° inclined planes at an angle equal to or larger than the critical angle of total internal reflection without fail, and being prevented from being transmitted through the one or more 45° inclined planes by being totally reflected by the one or more 45° inclined planes.