This paper presents a self-organized microsphere array to enhance image brightness and contrast of a volumetric 3D display. This display, using a swept-volume technique, exhibits 3D images by 2D projective-image-frame sweeping. These images are projected from a programmable LED array and a focusing lens system. The sweeping screen consists of a self-organized metallic microsphere array, which acts like a reflective screen to enhance the image brightness and contrast from a multitude of viewing directions. The voxels can be controlled by manipulating the frequency of flashing LEDs and the sweeping screen. The experiment results successfully demonstrate 500 voxels in a 6cm3 tetragonal imaging space. This paper also shows the effectiveness of using a metallic self-organized microsphere array to increase the brightness of voxels. Compared to the voxels generated by original reference screen, it can increase image brightness up to 300%.