An actuator has a first electrode, a piezoelectric body, and a second electrode that are on a surface of a substrate in this order and an insulating film covering at least a side surface of the piezoelectric body. The actuator has a plurality of slanted surfaces slanted relative to the substrate at an end portion of a surface of the first electrode which is opposite from the substrate, and an angle between the substrate and a first slanted surface of the plurality of slanted surfaces which is farthest away from the substrate is smaller than an angle between the substrate and any other one of the slanted surfaces.

A piezoelectric element includes: a first electrode; a second electrode; and a piezoelectric layer provided between the first electrode and the second electrode and including a plurality of layers containing a complex oxide having a perovskite type structure containing potassium, sodium, and niobium, in which an X-ray diffraction method is used to measure asymmetric reflection of the piezoelectric layer in a range in which sin.sup.2.sub. is 0 or more and 0.7 or less, being a tilt angle, an obtained peak is separated into a high-angle-side peak and a low-angle-side peak, a lattice constant in a thickness direction of the piezoelectric layer is obtained based on the low-angle-side peak, and in a case where a plurality of the lattice constants are plotted for the range, when a plurality of plots are linearly approximated by a least squares method, a slope of an approximate straight line is 0.002 or less.

An imaging device includes a two dimensional array of piezoelectric elements. Each piezoelectric element includes: a piezoelectric layer; a bottom electrode disposed on a bottom side of the piezoelectric layer and configured to receive a transmit signal during a transmit mode and develop an electrical charge during a receive mode; and a first top electrode disposed on a top side of the piezoelectric layer; and a first conductor, wherein the first top electrodes of a portion of the piezoelectric elements in a first column of the two dimensional array are electrically coupled to the first conductor.

A MEMS device and a method for operating a MEMS device are provided. The MEMS device comprises a piezoelectric transducer element having at least a first piezoelectric transducer region and a deflectable structure, wherein the deflectable structure comprises the piezoelectric transducer element. The MEMS device further comprises a control circuitry configured to readout at least a first sensor signal from the first region of the piezoelectric transducer element based on a deflection of the deflectable structure. The control circuitry is further configured to determine a control signal from the readout first sensor signal, wherein the control signal has a counteracting effect to the deflection of the deflectable structure when provided to the piezoelectric transducer element. The control circuitry is configured to provide the control signal to the piezoelectric transducer element for counteracting the deflection of the deflectable structure.

Provided are a driver unit of a headphone, in which, in a case where a driver unit including a piezoelectric film having a formed curved portion is applied to the headphone, deformation of the curved portion of the piezoelectric film in a case of wearing the headphone can be suppressed, and deterioration in sound quality can be suppressed; and a headphone. The driver unit includes a piezoelectric film which has a piezoelectric layer consisting of a polymer-based piezoelectric composite material containing piezoelectric particles in a matrix containing a polymer material and electrode layers provided on both surfaces of the piezoelectric layer, and a perforated plate having at least one through-hole, in which the piezoelectric film has a curved portion which is formed to protrude to one main surface side and to be recessed to the other main surface side, the perforated plate is laminated on a concave surface side of the curved portion of the piezoelectric film, and in the through-hole, a first air chamber defined by the concave surface of the piezoelectric film and the perforated plate communicates with an outside.