| 摘要 |
A vibration control unit inputs an electrical signal to a vibrating member to generate, in a light-transmitting region of a dust-screening member, vibration forming a plurality of ridges of peaks defining a closed loop around a virtual intersection at which a virtual vibrational axis passing the half-length point of the vibrating member intersects with a virtual vibrational axis passing the half-length point of the dust-screening member. For example, the vibration is vibration whose peak including the virtual intersection gradually increases in terms of amplitude as the amplitude of the peak approaches the virtual intersection, and becomes the largest in terms of amplitude at the virtual intersection. The dust-screening member and the vibrating member have the following relation: 1.2≦̸Ts/Tg≦̸1.6, where Tg is the thickness of the thickness of the dust-screening member, and Ts is the thickness of the vibrating member. |
