In addition to light loss, there are two other important design challenges that engineers need to address when trying to optimize lightpipe designs: uniformity and light bleeding conditions. Uniformity refers to the lightpipe’s ability to display uniform and consistent light across the exit surface. Light voids are usually referred to as hot or dark spots. Dark spots are commonly present when an incorrect number of lightsource elements, power, or brightness is used in the setup. Dark spots are addressed by optimizing lightsource positioning, having the correct number of lightsource elements and brightness levels, and by adding a surface finish and/or light diffusion additives to the lightpipe material. These small changes ensure proper light distribution across the lightpipe body.  Another predominant design challenge is light bleeding, also known as light pollution. This occurs when the refractive property of the lightpipe body is unable to correctly interact with the lightsource element and its brightness specification. The lightpipe essentially is unable to contain and transmit the light, resulting in visible light bleeding onto the adjacent exit surfaces. This condition is usually addressed by optimizing the mechanical geometry on the lightpipe, and by selecting corresponding lightsource properties to match the refractive index of the optical material.