Although many of recent mobile phones are integrally equipped with a camera, it is difficult with the employment of the camera installed in such a mobile phone to take a clear picture of image especially when a subject exists in a dark place because of the performance of the camera. Namely, although the image pickup performance of the camera depends largely on brightness as well as color rendering of flash illumination to be emitted from a flash mounted on the mobile phone, no one has succeeded as yet to develop such a flash which is capable of exhibiting a sufficient brightness and satisfactory color rendering for enabling a clear picture of image to be taken under such a dark condition.
In recent years, in view of the possibility of reducing the size and weight of a portable terminal unit, much attention has been paid to the employment of an LED flash. The LED flash to be mounted on a portable terminal unit is required, first of all, to be excellent in brightness. Because of this, a plurality of LED chips are generally employed for the purpose of flash illumination at present. However, since the capacity of battery to be employed therein is limited, the efficiency of each LED chip is desired to be as high as possible. Furthermore, since the direction of light toward a subject to be photographed, i.e., the directivity of brightness is a key if the LED chip is to be employed for the purpose of flash illumination, the luminescence intensity (cd) of the LED chip is one of the important characteristics thereof.
Therefore, there have been proposed various ideas such, for example, as; an idea to dispose a reflection plate close to and around an LED chip for the purpose of enhancing the luminescence intensity thereof; an idea to dispose a plurality of LED chips so as to circularly surround one LED chip (see, for example, JP-A 2005-158958); and an idea to dispose a plurality of LED chips with centers thereof being linearly arrayed (see, for example, JP-A 2005-109212 and JP-A 10-22529). In spite of these proposals, no one has succeeded as yet to develop such a flash which is capable of exhibiting satisfactory brightness.