Toner-density calculating method, reflective optical sensor, reflective optical sensor device, and image forming apparatus

A toner-density detecting method implemented on a toner image forming apparatus, the toner-density calculating method comprising:

• forming a predetermined toner pattern on a surface of a supporting member that moves in a first direction;
• emitting a detection light onto the supporting member with a light-emitting unit;
• receiving a reflected light reflected from at least one of the supporting member and the toner pattern with a light-receiving unit;
• and
• detecting a toner density of the toner pattern based on a difference between a reflection property of the supporting member to the detection light and a reflection property of the toner pattern to the detection light, wherein
• the light-emitting unit includes M number of light-emitting elements emitting light having the same wavelength and aligned in a third direction that is inclined to the first direction, where M is equal to or larger than three, wherein the light-emitting elements emit the detection light so that M number of light spots fall on the supporting member in such a manner that a distance between adjacent light spots in a second direction that is perpendicular to the first direction in a plane of the supporting member is equal to or smaller than a width of the toner pattern in the second direction,
• the light-receiving unit includes N number of light-receiving elements that receive the reflected light from at least one of the supporting member and the toner pattern, where N is equal to or larger than three, wherein the light-receiving elements are aligned, opposed to the supporting member, in a single direction, corresponding to the light-emitting unit, and
• the detecting includes detecting the toner density from outputs of the light-receiving elements in the light-receiving unit while causing light emitting elements in the light-emitting unit to emit light in the emitting.