Illumination device, biometric authentication apparatus, and biometric authentication program

摘要

An illumination device includes a light source provided on a surface of a substrate and configured to emit light, and a diffraction optical element having a plurality of diffraction gratings with different pitch and rotating direction, and configured to diffract the light into illumination light that illuminates an illumination region of an illuminating target. The illuminating region is larger than an area occupied by the diffraction optical element and the light source provided on the surface of the substrate.