Abstract: An acoustic wave filter includes a substrate having voids formed therein; a first resonator disposed on one or more of the voids, and a second resonator disposed on other of the voids. A first trimming layer is provided in the first resonator, and a second trimming layer is provided in the second resonator. The second trimming layer is formed of a material having an etching rate for a given etchant different from that of the first trimming layer.

Abstract: Examples provide a piezoelectric energy harvester and a wireless switch including the same. The piezoelectric energy harvester includes a pressure transmission part situated between a pressing plate and a piezoelectric body, so as to transmit a uniform amount of pressure to the piezoelectric body, thereby generating a constant level of energy. In addition, a wireless switch uses energy generated in the piezoelectric energy harvester as its driving power, thereby transmitting radio frequency (RF) communications signals to an external electronic device to control the operation of the electronic device.

Abstract: There is provided an optical system including a first lens, a second lens, a third lens, a fourth lens including a negative refractive power, a fifth lens including negative power, and a sixth lens. An image-side surface of the fourth lens is convex in a paraxial region. An image-side surface of the fifth lens is convex in the paraxial region. The sixth lens includes an image-side surface that is concave in the paraxial region. The first to sixth lenses are sequentially disposed from an object side to an image side.

Abstract: An LED diode package includes a heat connecting part for mounting a light emitting part on an upper surface thereof, frames electrically connected to the light emitting part while holding the heat connecting part and a molded part fixing the heat connecting part and the frames together. The light emitting part generates light in response to current applied thereto, and the upper surface of the heat connecting part is protruded beyond an upper surface of the molded part to a predetermined height. This can optimize the unique beam angle of the light source thereby to maximize lighting efficiency as well as prevent overflow of the encapsulating material in the assembling process of the lens, which may otherwise soil adjacent components.

Abstract: A device for etching the backside of a wafer is disclosed. The etching device directly feeds an etchant to a target wafer without using any medium, such as a conventional absorption fabric, thus uniformly etching the backside of the wafer, and prevents the wafer from coming into contact with the etchant during the removal of the wafer from the device, thus almost completely protecting the wafer from any damage. This etching device consists of a cylindrical housing having a conical bottom wall, and an annular etching dam seated in the housing while forming an etchant collecting chamber and an etching bath. An etchant supply unit is provided on the conical bottom wall of the housing. At least one first etchant discharging part communicates the etching bath with the collecting chamber, while at least one second etchant discharging part communicates the etchant collecting chamber with the outside.