A system may determine an extent to which a document is selected when the document is included in a set of search results, generate a score for the document based, at least in part, on the extent to which the document is selected when the document is included in a set of search results; and rank the document with regard to at least one other document based, at least in part, on the score. The imaging system may include a controller configured to capture a series of holograms by powering a light source of the optical device to illuminate an object, wherein light from the light source is collimated onto the object through an aperture of the optical device. The method includes the steps of chemically combining a crystalline carbon and an amorphous carbon precursor; removing remaining amorphous carbon precursor not reacted in the chemical combination; and heat-treating a chemical combination material of graphite and the amorphous carbon precursor obtained in the chemical combination. The terminal connective portion 30a is connected with an electrode terminal 40 led out of a printed circuit board 13 of a lighting circuit 14 so that the conductive resin shell 30 and the lighting circuit 14 are electrically connected.