OPTICAL MASK

PURPOSE:To facilitate production by integrating and fixing many rod-shaped glass bodies, each one of which has internally an optical density distribution and which are in the arrayed state, by filling the spacings therebetween with a light shieldable material. CONSTITUTION:This optical mask is constituted of the many rod-shaped glass bodies 1 each of which has internally the optical density distribution and is made to a circular columnar shape and the light shielding part 2 consisting of the light shielding material enclosing the spacings between the glass bodies. The optical density of, for example, the light shielding part 2 is 2.0 and the optical densities of the respective glass bodies 1 make secondary distribution so as to be 0 in the central part and about 2.0 in the peripheral part. Since the optical density distributions are formed in the inside unlike the optical mask of the conventional type, the possibility that the optical density distributions are disturbed by the wear arising at the time of mask alignment is obviated and the mask withstands repetitive uses.