Abstract: A light emitting diode module for a line light source includes a circuit board having a wire pattern formed thereon and a plurality of LED chips directly mounted and disposed in a longitudinal direction on the circuit board and electrically connected to the wire pattern. The module also includes a reflecting wall installed on the circuit board to surround the plurality of LED chips, reflecting light from the LED chips. The module further includes a heat sink plate underlying the circuit board to radiate heat generated from the LED chip.
Abstract: A width of a core in an optical waveguide is decreased in accordance with a value of a predetermined equation, as a distance of a position of the core to the center position thereof is decreased. Consequently, a rectangular spectrum property having no ripple is obtained on a lower wavelength side in a reflection grating. In addition, the width of the core is changed at the position Z in the direction of light propagation, while a UV light is radiated to the core, so that a periodically striated distribution of refractive indices having an envelope which is changed in accordance with a value of ".vertline.sin(C.multidot.Z).vertline./.vertline.C.multidot.Z.vertline." is formed in the core of the optical waveguide, and a phase of a light to be propagated in the direction of the light propagation is shifted at the position Z as defined below by .pi..Z=m.pi./C(m=. . . ,-3,-2,-1,1,2,3, . . )Thus, a rectangular spectrum property is obtained in a low reflection grating.