A medium transport device includes a medium transport path for transporting a medium, and a medium detection unit that detects a medium by using detection light intersecting the medium transport path. the medium detection unit is a part constituting an optical path of the detection light, and includes a first optical component positioned on a first side of the medium transport path, and a second optical component positioned on a second side with the medium transport path interposed therebetween, and the second optical component is accommodated in a recess formed in a wall face extending in a direction intersecting a path surface of the medium transport path.

A sheet behavior monitor for a sheet processor includes: a folding machine processing a sheet; and a camera taking an image once for each signature (Wb) folded by the folding machine. The camera takes every image at a folding machine rotation phase different from that of the image immediately before taken.

A sheet behavior monitor for a sheet processor includes: a folding machine processing a sheet; and a camera taking an image once for each signature (Wb) folded by the folding machine. The camera takes every image at a folding machine rotation phase different from that of the image immediately before taken.

An image forming apparatus, having a housing with an opening, an image forming unit, a path to guide a recording medium toward the opening, a reversible roller disposed in the path, and an intermediate reversible roller disposed between the image forming unit and the reversible roller, is provided. A rotating direction of the reversible roller is switchable between a first rotating direction and a second rotating direction opposite from the first rotating direction. A circumferential speed of the reversible roller is switchable between a predetermined circumferential speed and none. A rotating direction of the intermediate reversible roller is switchable between a third rotating direction and a fourth rotating direction opposite from the third rotating direction. The circumferential speed of the reversible roller in the first rotating direction is reduced to be lower than the predetermined circumferential speed while the intermediate reversible roller is rotating in the third rotating direction.

An image forming apparatus, having a housing with an opening, an image forming unit, a path to guide a recording medium toward the opening, a reversible roller disposed in the path, and an intermediate reversible roller disposed between the image forming unit and the reversible roller, is provided. A rotating direction of the reversible roller is switchable between a first rotating direction and a second rotating direction opposite from the first rotating direction. A circumferential speed of the reversible roller is switchable between a predetermined circumferential speed and none. A rotating direction of the intermediate reversible roller is switchable between a third rotating direction and a fourth rotating direction opposite from the third rotating direction. The circumferential speed of the reversible roller in the first rotating direction is reduced to be lower than the predetermined circumferential speed while the intermediate reversible roller is rotating in the third rotating direction.

A sheet stacking apparatus, including: a movable stack portion on which sheets are to be stacked; a detection portion configured to detect whether or not a topmost sheet of sheets stacked on the stack portion is positioned at a predetermined position; and a control portion configured to position the topmost sheet at the predetermined position based on a detection result of the detection portion, wherein in a case where the control portion moves the stack portion at a first speed so that a topmost sheet on the stack portion deviates from the predetermined position, the control portion moves the stack portion at a second speed lower than the first speed to position the topmost sheet at the predetermined position.

A conveyed object detection apparatus includes an optical sensor configured to receive light reflected by a conveyed object; a detection unit configured to use the optical sensor to acquire a detection result indicating a position, a moving speed, or a moved amount of the conveyed object in at least one of a conveyance direction in which the conveyed object is conveyed and a direction perpendicular to the conveyance direction, or a combination of the position, the moving speed, and the moved amount; and a setting unit configured to set an aperture value and an exposure time concerning the optical sensor based on the detection result.

A conveyed object detection apparatus includes an optical sensor configured to receive light reflected by a conveyed object; a detection unit configured to use the optical sensor to acquire a detection result indicating a position, a moving speed, or a moved amount of the conveyed object in at least one of a conveyance direction in which the conveyed object is conveyed and a direction perpendicular to the conveyance direction, or a combination of the position, the moving speed, and the moved amount; and a setting unit configured to set an aperture value and an exposure time concerning the optical sensor based on the detection result.

A printing apparatus can prevent a print medium from buckling during discharging. In a case in which the print conveyance speed determined by the print mode is higher than or equal to a specified speed, the print medium after printing is conveyed to a discharging tray at the print conveyance speed, and in a case in which the print conveyance speed determined by the print mode is lower than the specified speed, the print medium after printing is conveyed to the discharging tray at the specified speed increased from the print conveyance speed.

A post-processing apparatus includes a post-processing unit configured to receive sheets from an image forming apparatus, perform processing on the received sheets, and then discharge the processed sheets through a discharge port. A sensor is configured to detect a presence of an object at the discharge port. The sensor includes a first light emitter on a first side of the discharge port that is positioned to emit a light across a width of the discharge port, a reflector on a second side of the discharge port opposite the first side in a first direction, and a first light receiver positioned to receive light of the first light emitter from the reflector. A controller is configured to terminate the processing on the received sheets by the post-processing unit when the sensor detects the presence of the object at the discharge port.