Image forming apparatus

An image forming apparatus, comprising:

• an image carrying member that includes a photosensitive layer formed on a surface thereof;
• a charging device that charges the surface of the image carrying member;
• an exposure device that exposes, to light, the surface of the image carrying member having been charged by the charging device, thereby forming an electrostatic latent image with attenuated charge;
• a developing device that includes a developer carrying member carrying a developer including toner, and that develops the electrostatic latent image having been formed on the image carrying member into a toner image;
• an intermediate transfer belt to which the toner image having been formed on the image carrying member is primarily transferred;
• a cleaning brush that removes toner remaining on the intermediate transfer belt;
• an image density sensor that detects density of the toner image having been primarily transferred onto the intermediate transfer belt;
• and
• a control portion that executes calibration to correct image density based on density of a reference image having been detected by the image density sensor,
• wherein
• the calibration includes:
• a first adjustment process of detecting density of a first reference image formed on the intermediate transfer belt and adjusting an image forming condition based on a detection result;
• a first bare-surface-measurement process of detecting a first-reference-image formation area using the image density sensor when the intermediate transfer belt has rotated once or more after execution of the first adjustment process;
• and
• a second adjustment process of detecting, when the intermediate transfer belt has rotated once after execution of the first bare-surface-measurement process, density of a second reference image formed on the first-reference-image formation area, and changing, based on a detection result, an image forming condition that is different from the image forming condition adjusted in the first adjustment process, and
• in a case where a fluctuation range of an output waveform of the image density sensor in the first bare-surface-measurement process is equal to or less than a threshold value, the control portion determines that a surface condition of the intermediate transfer belt is normal, and executes the second adjustment process.