A projector includes: a spatial light modulator, which receives pattern data, representing a pattern to be formed on a projection plane, and which spatially modulates incoming light in accordance with the pattern data; and a projection optical system for projecting the light, which has been reflected from the spatial light modulator, onto the projection plane in a reduced size. A one-piece ring gear having a diameter less than or equal to the diameter of the grinding tube is attached to the small diameter end of a discharge cone of the grinding tube. Preferred embodiments are disclosed in which a removable cover is attached to the thermal compound for further improved protection during handling. The first intermetal dielectric layer includes at least one via hole extending to the upper electrode layer.