Patent ID: 8260164

Claim:
A toner-density calculating 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 calculating 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 aligned in a third direction that is inclined to the first direction, where M is equal to or larger than three, 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 reflected from at least one of the supporting member and the toner pattern, where N is equal to or larger than three, the light-receiving elements are aligned, opposed to the supporting member, in a single direction, corresponding to the light-emitting unit, the emitting includes emitting the detection light sequentially from the M light-emitting elements, and the calculating includes when a first light-emitting element emits the detection light, categorizing an output of a first light-receiving element corresponding to the first light-emitting element to a specular reflection output representing specular reflection light, and categorizing outputs of non-corresponding light-receiving elements to the first light-emitting element to diffuse reflection outputs representing diffuse reflection light; and calculating the toner density based on categorized outputs of the light-receiving elements.