Abstract: An optical device includes: a lens including a first lens portion having a first curved surface with a first curvature and a second lens portion having a second curved surface corresponding to the first curved surface; a display device disposed on a first side surface of the lens; a convex lens disposed between the first side surface of the lens and the display device; and a reflector disposed on the first curved surface of the first lens portion of the lens, the reflector configured to reflect light of the display device refracted by the convex lens toward a user's eye.

Abstract: Provided is an acoustic sensor for measuring a sound wave propagating through a gas such as air or a fluid such as water and an elastic wave propagating through a solid medium, and more particularly, an acoustic sensor with a piezo-arrangement film capable of detecting frequencies in a broad band or amplifying a signal at a specific frequency by comparting a waveguide into an upper waveguide and a lower waveguide by means of a compartment diaphragm and arranging piezoelectric sensors on the compartment diaphragm in several forms. The acoustic sensor can be utilized as a resonant acoustic sensor in which the piezoelectric sensors are arranged on the compartment diaphragm in the same form so that a signal at a specific frequency overlaps for high sensibility or a broadband acoustic sensor in which the piezoelectric sensors are arranged in a different form to detect frequencies in a broad band.

Abstract: Provided is an acoustic sensor for measuring a sound wave propagating through a gas such as air or a fluid such as water and an elastic wave propagating through a solid medium, and more particularly, an acoustic sensor with a piezo-arrangement film capable of detecting frequencies in a broad band or amplifying a signal at a specific frequency by comparting a waveguide into an upper waveguide and a lower waveguide by means of a compartment diaphragm and arranging piezoelectric sensors on the compartment diaphragm in several forms. The acoustic sensor can be utilized as a resonant acoustic sensor in which the piezoelectric sensors are arranged on the compartment diaphragm in the same form so that a signal at a specific frequency overlaps for high sensibility or a broadband acoustic sensor in which the piezoelectric sensors are arranged in a different form to detect frequencies in a broad band.

Abstract: A method for controlling a call reception operation in a wide area radio pager, which is capable of providing a continued stable radio call service to the radio pager without generating errors in receiving radio call signals even when the user of the radio pager is positioned in a boundary area between adjacent areas during his area movement. Radio call signals, which are transmitted from a base station, are carried with identification data containing information associated with an area reported to the communication company end as a destination area to which the user of the associated wide area radio pager is to move. Based on such area movement ID data, the radio pager recognizes the destination area to which the user of the radio pager is to move.