Image-forming apparatus and method for image recording on two sides of a medium using a positioning mark

An image forming apparatus, comprising:

• a first image bearing member;
• a second image bearing member;
• means for forming a latent image of an image on the first image bearing member;
• means for visualizing the latent image formed on the first image bearing member into a visual image;
• and
• first means for transferring visual images from the first image bearing member onto the second image bearing member and onto a second side of a record medium;
• wherein a latent image of a positioning mark is formed with the means for forming a latent image on the first image bearing member and is visualized to a visual image of the positioning mark by a second means for visualizing, and the visual image of the positioning mark is transferred from the first image bearing member to the second image bearing member by the first means for transferring to form the positioning mark on the second image bearing member at a position outside an image forming area having a size corresponding to that of a maximum size image that can be formed on the recording medium useable with the image forming apparatus and containing a first side visual image thereon transferred by the first transfer means from the first image bearing member for transferring from the image forming area onto a first side of the recording medium,
• wherein a second side visual image formed on the first image bearing member by the means for forming a latent image and the means for visualizing is transferred from the first image bearing member onto the second side of the recording medium by the first means for transferring and the first side visual image is transferred from the image forming area onto a first side of the recording medium by a second means for transferring visual images, so that the first and second side visual image are obtained on the first and second sides of the recording medium, respectively, and
• wherein when forming the first side and second side visual images on the first and second sides of the recording medium, an image forming operation is controlled according to detection of the positioning mark on the second image bearing member with a means for detecting the positioning mark such that positions of the first side and second side visual images on the first and second sides of the recording medium coincide with which other.

An image forming method for obtaining a first side visual image and a second side visual image on a first side and a second side of a recording medium by p transferring the first side visual image from a first image bearing member to a second image bearing member and from the second image bearing member onto the first side of the recording medium, and transferring the second side visual image from the first image bearing member to the second side of the recording medium, the method comprising the steps of:

• forming the first side visual image in an image forming area on the second image bearing member, the image forming area having a size corresponding to that of a maximum recording medium useable with the image forming apparatus;
• forming a positioning mark on the second image bearing member at a position outside the image forming area;
• detecting the positioning mark;
• and
• controlling formation of the second side visual image on the second side of the second medium according to detection of the positioning mark such that positions of the first side and second side visual images on the first and second sides of the recording medium coincide with each other.