Patent ID: 8746892

Claim:
An illuminating optical system, comprising: a substantially rectangular-shaped light source that includes a light emitting surface with a split pattern formed therein by a splitting line, the splitting line extending along a predetermined direction and splitting the light emitting surface into a plurality of separate areas; an illumination-target member that includes a rectangular radiation-target area ranging along a lengthwise direction in which longer sides thereof extend and along a crosswise direction in which shorter sides thereof extend; and an optical member that condenses light departing the light emitting surface and radiates the condensed light toward the radiation-target area by assuming different image formation positions of the light emitting surface along the longer sides and along the shorter sides of the radiation-target area so as to enlarge the split pattern at different magnification factor along the longer sides and the shorter sides, wherein: the light source is disposed so that the shorter sides of the radiation-target area are set substantially parallel to the predetermined direction, so as to reduce an extent of uneven illumination attributable to an image of the split pattern at the light emitting surface of the light source formed at the illumination-target member.