Abstract: The present invention provides an optical multiplexer that can be downsized and includes a directional coupler capable of being fabricated with stable quality and accuracy. The present invention further provides an image projector including the optical multiplexer. The optical multiplexer includes: input waveguides for respectively receiving a plurality of visible light beams of different wavelengths; a directional coupler for multiplexing the plurality of visible light beams; and an output waveguide for outputting the multiplexed light. At least one of the input waveguides connected to the directional coupler and the output waveguide have a tapered structure. Therefore, the optical multiplexer can be downsized by reducing its overall length and can be fabricated with stable quality and accuracy by reducing a decrease in multiplexing efficiency caused by an error in the width of an optical coupling waveguide.

Abstract: An object of the present invention is to provide a punching method using a punch, which makes it possible to effectively improve the durability of a tooth portion of the punch. In a punching method using a punch for forming a through-hole in a workpiece by punching the workpiece using a punch, at least a tooth portion of the punch is made substantially solid when the workpiece is punched by the punch, and the tooth portion is made substantially hollow, thereby a diameter of the tooth portion is reduced by a reaction force received from the workpiece, when the workpiece is separated from the punch after the punching of the workpiece.

Abstract: An object of the present invention is to provide a punching method using a punch, which makes it possible to effectively improve the durability of a tooth portion of the punch. In a punching method using a punch for forming a through-hole in a workpiece by punching the workpiece using a punch, at least a tooth portion of the punch is made substantially solid when the workpiece is punched by the punch, and the tooth portion is made substantially hollow, thereby a diameter of the tooth portion is reduced by a reaction force received from the workpiece, when the workpiece is separated from the punch after the punching of the workpiece.