BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a vibration device for dust removal and also to an imaging device equipped with such a vibration device. More particularly, the present invention relates to a vibration device for dust removal that is designed to remove foreign objects such as dusts adhering to the surfaces of the optical parts incorporated in an imaging device such as a digital camera or an image reading device such as a scanner by means of vibrations and also to an imaging device equipped with such a vibration device.

Description of the Related Art

An imaging device such as a digital camera for picking up and recording an image by converting an image signal into an electric signal receives an imaging light flux by means of the image pick up device, which may typically be a CCD (charge coupled device) or a CMOS (complementary metal oxide semiconductor) it comprises. Then, the photoelectric conversion signal output from the image pickup device is converted into image data, which image data is then recorded in a recording medium such as a memory card. In such an imaging device, a cover glass, an optical low pass filter, an infrared absorption filter and other parts are arranged in front (on the subject side) of the image pickup device to form an image pickup unit there.

In an imaging device of the above-described type, when foreign objects such as dusts adhere to any of the surfaces of the cover glass and the filters of the image pickup unit, those foreign objects block the incident light flux and are picked up as black spots in the recorded image. Particularly, in the case of a digital single-lens reflex camera, the dusts that are produced when the shutter, the quick return mirror and/or some other part arranged near the image pickup unit is mechanically driven to operate can adhere, if partly, to any of the surfaces of the cover glass and the filters. Additionally, when the lens is being replaced, foreign objects such as dusts can get into the inside of the camera main body by way of the opening of the lens mount and adhere to any of the surfaces of the cover glass and the filters. However, when each of the cover glass and the filters is equipped with a piezoelectric element and the piezoelectric element is made to operate as a vibrating plate that give rise to elastic vibrations (to be referred to as flexural vibrations hereinafter) in the thickness direction, it can be made to operate as a dust removal device for removing the dusts adhering to the surfaces thereof. Each of Japanese Patent No. 4,724,584 and Japanese Patent Application Laid-Open No. 2009-215111 discloses a dust removal device of the above-identified type, an imaging device equipped with such a dust removal device and an image reading device also equipped with such a dust removal device.

More specifically, Japanese Patent No. 4,724,584 discloses a device for removing the dusts adhering to the surfaces of each of the optical parts (the low pass filter, the infrared absorption filter) of an imaging device by providing the optical part with a piezoelectric element and causing the piezoelectric element to give rise to flexural vibration waves in the thickness direction of the optical part. PZT (lead zirconate titanate), which is a typical piezoelectric ceramic material, is more often than not employed as the piezoelectric material of such piezoelectric elements. However, since there is deep concern over that the lead contained in PZT as principal ingredient thereof adversely affects the environment, it is highly desirable to use a piezoelectric material that does not contain any lead for such piezoelectric elements. Japanese Patent Application Laid-Open No. 2009-215111 discloses the use of a lead-free piezoelectric material such as BZT-BCT (barium calcium titanate zirconate) to meet the demand for such lead-free piezoelectric materials.

SUMMARY OF THE INVENTION

Thus, in an aspect of the present invention, there is provided a vibration device comprising a vibrating member having at least n (n≥2) piezoelectric elements arranged on a vibrating plate, each of the piezoelectric elements being formed by using a lead-free piezoelectric material and electrodes, wherein, if the temperature that maximizes the piezoelectric constant of the piezoelectric material of each of the n piezoelectric elements is expressed as Tm(m being a natural number from 1 to n), at least two of T1through Tndiffer from each other.

Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.

