Toner position detecting method and reflective optical sensor and an image forming apparatus

A light-emitting unit includes M (Mg3) number of light-emitting elements. A light-receiving unit includes N (Ng3) number of light-receiving elements that receive a reflected light from at least one of a supporting member and a toner pattern. The toner pattern is formed on a surface of the supporting member. A detection light is emitted onto the supporting member from the light-emitting unit. A reflected light reflected from at least one of the supporting member and the toner pattern is received by the light-receiving unit. A position of the toner pattern on the supporting member is detected based on outputs of the light-receiving elements.