Patent ID: 8396385

Claim:
A toner-density calculating method used in an image forming method for forming an image with toner, the toner-density calculating method comprising: forming a predetermined toner pattern on a supporting member that moves in a predetermined sub-direction; causing a light-emitting unit to illuminate the supporting member with detection light; receiving, at a light-receiving unit, the detection light reflected by the supporting member and/or the toner pattern; and calculating the toner density on a basis of difference between reflecting characteristics of the supporting member for the detection light and reflecting characteristics of the toner pattern for the detection light, wherein the light-emitting unit includes M number of light-emitting elements (M≧3) that emit the detection light, wherein the light-emitting elements are arranged in a direction intersecting with the sub-direction in such a manner that M number of spots of the detection light fall on the supporting member, and a distance between adjacent spots in a direction perpendicular to the sub-direction is less than or equal to a length of the toner pattern in the direction perpendicular to the sub-direction, the light-receiving unit includes N number of light-receiving elements (N≧3) that are arranged in a direction on a plane opposing to the supporting member, the light-receiving unit corresponding to the light-emitting unit so as to receive the detection light reflected by the supporting member and/or by the toner pattern, an output from each of the N number of the light-receiving elements, obtained when the M number of the light-emitting elements emit the detection light, is separated into an amount of specularly reflected light and an amount of diffusely reflected light, and the toner density is calculated on a basis of the amount of specularly reflected light and the amount of diffusely reflected light.