Vibrating device and image equipment having the same

An image equipment comprising:

• an image forming element having an image surface on which an optical image is formed;
• a dust-screening member which is shaped like a plate as a whole, has at least one side that is symmetric with respect to a symmetry axis, and has a light-transmitting region flaring in a radial direction from the center, facing the image surface and spaced therefrom by a predetermined distance;
• a vibrating member configured to produce vibration having an amplitude perpendicular to a surface of the dust-screening member, the vibrating member being provided on the dust-screening member, outside the light-transmitting region through which a light beam forming an optical image on the image surface passes;
• a sealing structure for surrounding the image forming element and the dust-screening member, thereby providing a closed space in which the image forming element and the dust-screening member that face each other;
• and
• a drive unit configured to drive the vibrating member to produce vibration Z(x,y) at the dust-screening member, the vibration being expressed as follows:
• Z(x,y)=Wmn(x,y)·cos(γ)+Wnm(x,y)·sin(γ)
• where Z(x,y) is vibration at a given point P(x,y) on the dust-screening member;
• m and n are positive integers including 0, indicating the order of natural vibration corresponding to a vibrational mode;
• W
• mn
• 
• (
• x
• ,
• y
• )
• =
• sin
• 
• (
• n
• 
• 
• π
• ·
• x
• +
• π
• 2
• )
• ·
• sin
• 
• (
• m
• 
• 
• π
• ·
• y
• +
• π
• 2
• )
• ;
• W
• nm
• 
• (
• x
• ,
• y
• )
• =
• sin
• 
• (
• m
• 
• 
• π
• ·
• x
• +
• π
• 2
• )
• ·
• sin
• 
• (
• n
• 
• 
• π
• ·
• y
• +
• π
• 2
• )
• ;
• and
• γ is +π/4 or ranges from −π/8 to −π/4, wherein
• the equipment has such a size that LP/LF is 0.5 or more, but less than 1, where LF is the length of the sides to which the vibrating member is arranged in a virtual rectangle having the same area as the surface of the dust-screening member and sides including the one side, and LB is the longitudinal length of the vibrating member of the sides parallel to the one side.