An image forming apparatus includes first and second light emitting units, a light receiving unit for receiving light of the first light emitting unit when it is reflected, and receiving light of the second light emitting unit when it is not reflected, to output a signal of a predetermined level, and a control unit for starting light emission of the first light emitting unit before a front end of a paper sheet reaches an area, stopping light emission of the first light emitting unit while starting light emission of the second light emitting unit before a rear end of the paper sheet passes the area, and detecting a length of the paper sheet based on time after the output signal becomes a predetermined level during light emission of the first light emitting unit until the output signal becomes the predetermined level during light emission of the second light emitting unit.

A medium conveying apparatus includes a moving mechanism to move the set guide, a guide pair including a first guide having a first opening and a second opening, and a second guide to regulate a vertical direction of the medium conveyance path, a light emitting element and a light receiving element located on an outside of the medium conveyance path with the first guide in between, and on the downstream side of the first opening and the second opening so as to be apart from the moving mechanism by a predetermined distance or more in the medium conveying direction, a first light guide which is bent so as to guide a light emitted from the light emitting element to the first opening, and a second light guide which is bent so as to guide the light incident from the second opening to the light receiving element.

An image forming apparatus includes a first unit, a second unit fixed to the first unit at a portion upstream of the first unit in a conveyance direction in which the sheet is conveyed, and an electric board. In the image forming apparatus, a disposition of the electric board is restricted by the first unit and the second unit.

A sheet feeder includes a sheet tray, a feed roller, a sheet feed frame, a contact element, a guide frame, a photosensor, a shield, and a linkage. The feed roller feeds a sheet on the sheet tray. The sheet feed frame holds the feed roller. The contact element is pivotable relative to the sheet feed frame. The guide frame is disposed below the sheet feed frame. The photosensor includes a light emitter and a light receiver. The shield is movable between a light transmission position and a light shield position. The linkage connects the contact element and the shield such that the shield is movable as the contact element pivots. The light receiver receives the light emitted from the light emitter when the shield is at the light transmission position. The shield at the light shield position shields the light receiver from the light emitted from the light emitter.

A feed detection unit which detects a document which is fed is provided at a position between a pinching position at which a feed roller and a frictional force application portion pinch the document and an intersecting position at which a tangential line of the feed roller which is closer to a downstream side in a transport direction than the pinching position is perpendicular to a transport path in the transport direction, which is a different position from the feed roller in a width direction which intersects the transport direction.

A method for producing a steel tube including the step of the manufacturing a steel tube having an inner tube wall, an outer tube wall, and a free tube cross-section enclosed by the inner tube wall, wherein after the manufacturing, the steel tube includes at least one contaminant on the inner tube wall. After the manufacturing of the steel tube, the inner tube wall is cleaned by introducing liquid or solid CO.sub.2 into the free tube cross-section, and of applying the liquid or solid CO.sub.2 onto the inner tube wall to remove the contaminant therefrom.

A medium flattening method, when a medium is transported by being adhered to an adhesive layer which is on a surface of a transport belt, includes detecting a presence or absence of floating being generated in the medium on the transport belt using a sensor, executing a process for flattening to flatten the floating in the medium in the case where the floating exists, and transporting the medium, where the floating is eliminated using the process for the flattening, to a liquid discharge region of a liquid discharge section.

A sheet discharging apparatus includes a discharging portion configured to discharge a sheet, a supporting portion configured to support the sheet discharged by the discharging portion, a lifting portion configured to lift and lower the supporting portion, a transmissive sensor configured to output an output signal that changes in accordance with a position of an upper surface of the sheet supported by the supporting portion, a reflective sensor configured to output an output signal that changes in accordance with the position of the upper surface of the sheet supported by the supporting portion, and a controller configured to control the lifting portion and including a first determining portion configured to determine whether or not sheet detection by the transmissive sensor is possible and a second determining portion configured to determine whether or not sheet detection by the transmissive sensor is needed.

A medium carrying device includes a carrying part that carries a continuous print medium, a detection part that includes a light emitting part and a light receiving part arranged sandwiching a carrying path, and that detects the print medium carried on the carrying path according to a light amount that is received by the light receiving part, and a control part that controls operations of the carrying part and the detection part, wherein the control part sets a first emitted light amount of the emitted light of the light emitting part used in image formation to the print medium by performing a light amount measurement using the light emitting part and the light receiving part in a state where the print medium is carried to a first position, and sets a threshold light amount that is used in detecting a boundary position between the first region and the second region by the detection part through performing another light amount measurement by obtaining a receiving light amount of the light receiving part with the first emitted light amount and by determining the threshold light amount based on the receiving light amount in a state where the print medium is carried from the first position to another second position.

A sensing device is for sensing an outer surface of a roll of material. An infrared (IR) laser source is configured to direct IR laser radiation to the outer surface of the roll of material. A single photon avalanche diode (SPAD) detector is configured to receive reflected IR laser radiation from the outer surface of the roll of material. A controller is coupled to the IR laser source and the SPAD detector to determine a distance to the outer surface of the roll of material based upon a time-of-flight of the IR laser radiation.