Abstract: The present disclosure relates to a boron compound useful in an organic light-emitting diode and an organic light-emitting diode comprising same and, more particularly, to a boron compound represented by any one of [Chemical Formula A], wherein [Chemical Formula A] is as defined in the description.

Abstract: Disclosed is a polycyclic aromatic compound that can be employed in an organic layer of an organic electroluminescent device. Also disclosed is a highly efficient organic electroluminescent device including the polycyclic aromatic compound. The use of the polycyclic aromatic compound significantly improves the luminous efficiency of the device.

Abstract: An optical imaging system includes one or more lens surfaces divided into a plurality of areas, wherein adjacent areas among the plurality of areas are surfaces expressed by different equations, and light passing through each of the plurality of areas may be imaged on the image surface of the same image sensor. According to the disclosure, it is possible to form a composite lens surface by composing different shapes of curved surfaces on a lens surface constituting an optical imaging system and increase a design freedom of the optical imaging system. Further, it is possible to significantly improve optical characteristics of the optical imaging system, such as increasing the definition of image or the MTF property and the like. By applying plurality of such divided surface areas, it is also possible to optimize, synthesize, or manipulate the optical characteristics of the optical imaging system relevant to each interested field area.