Image forming apparatus

Image forming apparatus comprising:

• a movable image bearing member which carries a toner image;
• a first image forming unit, which includes a first photoreceptor, and the first photoreceptor is charged and exposed and then a toner image is developed and the first image forming unit forms a toner image to the image bearing member;
• a second image forming unit which is disposed further downward than the first image forming unit in a direction in which the image bearing member is moved, and which includes a second photoreceptor, and the second photoreceptor is charged and exposed and then a toner image is developed and the second image forming unit forms a toner image to the image bearing member;
• a detection member which is disposed further downward than the second image forming unit in the direction in which the image bearing member is moved, and which detects a toner image for adjustment which is formed on the image bearing member;
• an execution unit which is capable of executing a first detection mode and a second detection mode, the first detection mode is a mode in which the toner image for adjustment is formed on the image bearing member by the first image forming unit, then the toner image for adjustment on the image bearing member is carried facing an area of the second photoreceptor which has a first electrical potential and is not developed, the toner image for adjustment on the image bearing member is detected by the detection member, and a second detection mode is a mode in which the toner image for adjustment is formed on the image bearing member by the first image forming unit, then the toner image for adjustment on the image bearing member is carried facing an area of the second photoreceptor which has a second electrical potential and is not developed, the toner image for adjustment on the image bearing member is detected by the detection member, the absolute value of the second electrical potential is smaller than the absolute value of the first electrical potential;
• and
• an adjustment unit which adjusts an image formation condition for image formation of the first image forming unit, in accordance with the detection result of the first detection mode performed before the image formation, regarding among images corresponding to the toner images formed by the first image forming unit during image formation an image in which a toner image formed on the image bearing member is not overlapped a toner image formed in the second image forming unit, and in accordance with the detection result of the second detection mode performed before the image formation, regarding among images corresponding to the toner images formed by the first image forming unit during image formation an image in which a toner image formed on the image bearing member is overlapped a toner image formed in the second image forming unit.