Patent ID: 7278755

Claim:
An illumination apparatus comprising: an LED array including a plurality of light emitting diodes disposed in a two dimension; a first lens array including a plurality of first lenses in correspondence with the respective light emitting diodes, the first lens array emitting pieces of illumination light irradiated from the respective light emitting diodes to constitute pieces of collimated light in parallel with each other; and a superposing optical system comprising a second lens array which is opposed to the first lens array and includes a plurality of second lenses disposed in a two dimension, the superposing optical system splitting emitted light from the first lens array into a plurality of pieces of secondary illumination light by the second lens array and superposing the split respective pieces of secondary illumination light in a common illumination area to irradiate; wherein by making aligning patterns or aligning pitches of the first lens and the second lens differ from each other, respective in-face intensity distributions of the pieces of secondary illumination light emitted from the superposing optical system are made to be irregular so that the in-face intensity distributions are averaged in the common illumination area.