Image forming apparatus

An image forming apparatus comprising:

• a plurality of image forming devices corresponding to a plurality of colors,
• the plurality of image forming devices including a plurality of image bearers;
• a plurality of image output devices to form a plurality of latent pattern images on the plurality of image bearers,
• the plurality of image forming devices forming a plurality of visible pattern images from the plurality of latent pattern images;
• an endless conveyor;
• a transfer device to transfer the plurality of visible pattern images from the plurality of image bearers onto the endless conveyor;
• the endless conveyor conveying the plurality of visible pattern images in an image conveyance direction;
• a plurality of holders to hold the plurality of image forming devices interchangeable at a plurality of holding positions aligned in the image conveyance direction,
• the plurality of holding positions including a specific holding position;
• a detector to detect the plurality of visible pattern images on the endless conveyor;
• and
• circuitry to compare a first visible pattern image of the plurality of visible pattern images with a second visible pattern image of the plurality of visible pattern images to correct misalignment between the first visible pattern image and the second visible pattern image,
• the first visible pattern image being formed by one of the plurality of image forming devices held at the specific holding position and transferred onto the endless conveyor,
• the second visible pattern image being formed by another one of the plurality of image forming devices held at another holding position of the plurality of holding positions and transferred onto the endless conveyor.