Patent ID: 6987617

Claim:
A diffracting optical element in which a plurality of layers having a periodic relief pattern varying in height in a period are laminated in proximity to or in close contact with each other, comprising: a first layer, a relief pattern thereof being formed on a boundary with an air layer; a second layer, positioned in proximity to said first layer through the air layer without contacting said first layer; and a third layer, a maximum height of the relief pattern of said third layer being different from that of said first layer and equal to that of said second layer, and a direction of said third layer in which the height of the relief pattern varies in a period is equal to that of said first layer and opposed to that of said second layer; wherein material forming said first, second and third layers differ in dispersion from one another; and difference between maximum optical path lengths of light transmitting through said diffracting optical element is an integer multiple with wavelengths in a visible region.