Vibrating device and image equipment having the same

1. A vibrating device comprising:

a dust-screening member which is shaped like a plate as a whole and has at least one side that is symmetric to the X-axis that is a given axis of symmetry;

a vibrating member secured to the dust-screening member and configured to produce, at the dust-screening member, vibration having a vibrational amplitude perpendicular to a surface of the dust-screening member; 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 )= W mn ( x,y )·cos(γ)+ W nm ( 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

n

⁢

⁢

m

⁡

(

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; and

a ratio between a first bending rigidity along the X-axis of at least the dust-screening member and vibrating member in the section orthogonal to the X-axis at the intersection of the X- and Y-axes, to a second bending rigidity along the Y-axis of at least the dust-screening member in the section orthogonal to the Y-axis at the intersection is 0.4 or more, but less than 1.0, the Y-axis being orthogonal to the X-axis in a virtual rectangle which has the same area as the surface of the dust-screening member, and which has long sides including the one side of the dust-screening member.

2. The device according to claim 1 , wherein

γ is +π/4, and

the vibration produced at the dust-screening member by the drive unit is vibration such that peak ridges of the vibration having a vibrational amplitude perpendicular to the surface of the dust-screening member form closed loops.

3. The device according to claim 1 , wherein

γ ranges from −π/8 to −π/4, and

the vibration produced at the dust-screening member by the drive unit is vibration such that peak ridges of the vibration having a vibrational amplitude perpendicular to the surface of the dust-screening member form curves around a midpoint of the side which the dust-screening member has.

4. The device according to claim 1 , wherein

the vibrating member includes a piezoelectric element, and

the drive unit configured to supply a signal to the piezoelectric element to produce the vibration at the dust-screening member, the signal having a frequency that accords with a size and material of the dust-screening member.

5. The device according to claim 4 , wherein the drive unit configured to supply a signal to the piezoelectric element at prescribed time intervals, the signal changing in frequency, from a drive-start frequency to a drive-end frequency in increments of a given transmutation frequency, including the frequency that accords with the with size and material of the dust-screening member.

6. The device according to claim 1 , wherein a plurality of vibrating members are provided on the dust-screening member.

7. A vibrating device comprising:

a dust-screening member which is shaped like a plate as a whole and has at least one side that is symmetric to the X-axis that is a given axis of symmetry;

a vibrating member secured to the dust-screening member and configured to produce, at the dust-screening member, vibration having a vibrational amplitude perpendicular to a surface of the dust-screening member; 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 )= W mn ( x,y )·cos(γ)+ W nm ( 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

n

⁢

⁢

m

⁡

(

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; and

a ratio between a first bending rigidity along the X-axis of at least the dust-screening member in the section orthogonal to the X-axis at the intersection of the X- and Y-axes, to a second bending rigidity along the Y-axis of at least the dust-screening member in the section orthogonal to the Y-axis at the intersection is 0.4 or more, but less than 1.0, the Y-axis being orthogonal to the X-axis in a virtual rectangle which has the same area as the surface of the dust-screening member, and which has long sides including the one side of the dust-screening member.

8. 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 to the X-axis that is a given axis of symmetry, and has a light-transmitting region at least 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 )= W mn ( x,y )·cos(γ)+ W nm ( 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

m

⁢

⁢

n

⁡

(

x

,

y

)

=

sin

⁡

(

n

⁢

⁢

π

⁢

·

x

+

π

2

)

·

sin

(

m

⁢

⁢

π

⁢

·

y

+

π

2

⁢

)

;

W

n

⁢

⁢

m

⁡

(

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

a ratio between a first bending rigidity along the X-axis of at least the dust-screening member and vibrating member in the section orthogonal to the X-axis at the intersection of the X- and Y-axes, to a second bending rigidity along the Y-axis of at least the dust-screening member in the section orthogonal to the Y-axis at the intersection is 0.4 or more, but less than 1.0, the Y-axis being orthogonal to the X-axis in a virtual rectangle which has the same area as the surface of the dust-screening member, and which has long sides including the one side of the dust-screening member.

9. The equipment according to claim 8 , wherein

γ is +π/4, and

the drive unit produces at the dust-screening member vibration such that peak ridges of the vibration having a vibrational amplitude perpendicular to the surface of the dust-screening member form closed loops around an optical axis that passes the image surface of the image forming element.

10. The equipment according to claim 9 , wherein the sealing structure includes:

a holder arranged so as to achieve airtight sealing between the image forming element and the dust-screening member; and

a support member configured to secure the dust-screening member to the holder, the support member being arranged in a node region that has almost no vibrational amplitude perpendicular to a surface of the dust-screening member.

11. The equipment according to claim 8 , wherein

when γ is −π/8 to −π/4, and

the drive unit produces at the dust-screening member vibration such that peak ridges of the vibration having a vibrational amplitude perpendicular to the surface of the dust-screening member form curves surrounding a midpoint of the side which the dust-screening member has.

12. The equipment according to claim 11 , wherein the sealing structure includes:

a holder arranged so as to achieve airtight sealing between the image forming element and the dust-screening member; and

a support member configured to secure the dust-screening member to the holder, the support member being arranged in a node region that has almost no vibrational amplitude perpendicular to a surface of the dust-screening member.

13. The equipment according to claim 8 , wherein

the vibrating member includes a piezoelectric element, and

the drive unit configured to supply a signal to the piezoelectric element to produce the vibration at the dust-screening member, the signal having a frequency that accords with a size and material of the dust-screening member.

14. The equipment according to claim 13 , wherein the drive unit configured to supply a signal to the piezoelectric element at prescribed time intervals, the signal changing in frequency, from a drive-start frequency to a drive-end frequency in increments of a given transmutation frequency, including the frequency that accords with the with size and material of the dust-screening member.

15. The equipment according to claim 8 , wherein vibrating members including the vibrating member are opposed across a transmission region of the dust-screening member, through which light passes.

16. 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 to the X-axis that is a given axis of symmetry, and has a light-transmitting region at least 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 )= W mn ( x,y )·cos(γ)+ W nm ( 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

n

⁢

⁢

m

⁡

(

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

a ratio between a first bending rigidity along the X-axis of at least the dust-screening member in the section orthogonal to the X-axis at the intersection of the X- and Y-axes, to a second bending rigidity along the Y-axis of at least the dust-screening member in the section orthogonal to the Y-axis at the intersection is 0.4 or more, but less than 1.0, the Y-axis being orthogonal to the X-axis in a virtual rectangle which has the same area as the surface of the dust-screening member, and which has long sides including the one side of the dust-screening member.