A method of eliminating interference at an optical sensor of a mobile device that receives light from multiple light sources. The mobile device includes an optical navigation module having a cover and an illumination device disposed around the periphery of the cover. The optical navigation module includes an optical sensor that detects light reflected from an object contacting the cover. A processor receives electrical signals from the optical sensor and interprets movement of the object. The method reduces interference between the light source of the optical navigation module and the light source of the illumination device by controlling emission of light rays from each light source. The emission of light rays may be controlled based on timing, frequency and/or coding domains.