Optical element and optical system having the same

An optical element integrally formed from a transparent optical material, comprising:

• two refraction surfaces;
• a first reflection surface group having a plurality of internal reflection surfaces arrayed in a predetermined direction;
• a second reflection surface group opposing said first reflection surface group and having at least one internal reflection surface;
• and
• two side surfaces opposing each other in parallel to the predetermined direction,
• wherein light incident from one of the refraction surfaces is alternately reflected by the internal reflection surfaces of said first reflection surface group and the internal reflection surface of said second reflection surface group and is guided to the other refraction surface,
• wherein a width of at least one of the internal reflection surfaces of said first and second reflection surface groups in a direction in which said two side surfaces oppose each other is smaller than a distance between said two side surfaces in the direction in which said side surfaces oppose each other, and
• wherein said optical element further comprises portions having no optical function, which are formed between said two side surfaces and the internal reflection surface having the width smaller than the distance between said two side surfaces, said portions being adjacent to the internal reflection surface having the width smaller than the distance between said two side surfaces, and a shape of said portions being different from that of the internal reflection surface having the width smaller than the distance between said two side surfaces.