| abstract |
A multilayer film defining an optical axis, wherein the optical filter transmits 50% of light having a wavelength λ1 propagating along the optical axis, and the optical filter transmits 50% of light having a wavelength λ2 incident on the multilayer film at an angle of 30 degrees with respect to the optical axis, wherein |λ1 - λ2| is about 30 nm or less. |