Image forming apparatus capable of adjusting emission light amount of light-emitting portion, and light amount adjustment method

A light amount adjustment method executed in an image forming apparatus including:

• an image-carrying member which carries a toner image;
• a specific toner image forming portion which forms a toner image on the image-carrying member using toner of a predetermined specific color different from black;
• a first concentration sensor which includes a first light-emitting portion which emits light toward the image-carrying member and a first light-receiving portion which receives regular reflection light that is emitted from the first light-emitting portion and reflected by the image-carrying member and outputs an electric signal corresponding to a received light amount, the first concentration sensor being used to sense a toner concentration of a black toner image formed on the image-carrying member;
• and a second concentration sensor which includes a second light-emitting portion which emits light toward the image-carrying member and a second light-receiving portion which receives diffuse reflection light that is emitted from the second light-emitting portion and reflected by the image-carrying member and outputs an electric signal corresponding to a received light amount, the second concentration sensor being used to sense a toner concentration of a toner image in the specific color, that is formed on the image-carrying member, the light amount adjustment method comprising:
• a first adjustment step of adjusting an emission light amount of the first light-emitting portion based on an electric signal that is output from the first light-receiving portion and corresponds to regular reflection light reflected by a surface of the image-carrying member where toner has not adhered;
• a second adjustment step of adjusting an operation condition of the specific toner image forming portion based on a toner concentration of a first toner image in the specific color, that has a concentration smaller than a predetermined saturation concentration, the toner concentration of the first toner image being sensed by the first concentration sensor after the adjustment of the emission light amount of the first light-emitting portion in the first adjustment step;
• and
• a third adjustment step of adjusting an emission light amount of the second light-emitting portion based on an electric signal that is output from the second light-receiving portion and corresponds to diffuse reflection light reflected by a second toner image in the specific color, that has a predetermined reference concentration, the second toner image having been formed by the specific toner image forming portion after the adjustment of the operation condition in the second adjustment step.