US Patent 7615732 Solid state imaging device

Light guides are formed above each light receiving element. These light guides are made of a high refractive index material, and surrounded by a material of lower refractive index. The light guides are each made up of a light introduction region leading with a constant width from a light entrance surface, and a tapered reduced region leading from the light introduction region to a light exit surface. The light introduction region totally reflects the incident light toward the reduced region. The reduced region, owing to its tapered shape, surely directs the light onto a light receiving element, and prevents the light from entering charge transfer paths around the light receiving element.