The present invention provides an optical device, and the optical device comprises a luminous element and a gradient-index nanoparticle layer and scattering particles composed by particles stack with different refractive indexes and particle sizes. A first computing device communicates with a second computing device using a first set of tones. The second section defines a return mailing article having bottom, top and side edges, at least one of which is coincident with said first perforated line. First and second current ripple components corresponding to the first and time intervals, respectively, are estimated. A driven arm is provided with a rotation hole and is pivotally connected to the primary shaft hole of the fixed cutter base. The protective layer is configured to cover the base layer and the conductive layer, and includes an outer edge portion positioned on an outside of a periphery portion of the base layer.