Image forming device and control method for generating a plurality of toner images

A method of controlling an image forming device comprising a plurality of image generators each generating a toner image on a transfer belt, the method comprising:

• providing an image generation signal to the plurality of image generators;
• generating the plurality of toner images on the transfer belt according to the image generation signal;
• emitting light towards the transfer belt and sensing light reflected by the plurality of toner images;
• and
• performing, based on the sensed reflected light, at least one of concentration control of the plurality of toner images and alignment of the plurality of images,
• wherein the plurality of toner images are arranged on the transfer belt in parallel with each other, and an arrangement order of the plurality of toner images is identical to an arrangement order of the plurality of image generators, and
• wherein the plurality of toner images are generated simultaneously by the plurality of image generators.