We performed a 3-dimensional Monte Carlo simulation based on the Mie light scattering theory to investigate the photometric properties of a scattering polymer type light guide, that is known to give a very good brightness. The results reveal that the uniformity of the light guide with polymer scatterers abruptly decreases as the length of the light guide becomes larger than 20 cm. To improve the uniformity of the light guide, we employed a wedge-shaped light guide with dot patterns along with polymer scatterers. As a result, we were able to obtain a backlighting system satisfying a good uniformity and a high luminance at the same time.