A reflective optical sensor includes at least three light-emitting elements; a lighting optical system that guides light emitted from the light-emitting elements to a toner pattern; and at least three light-receiving elements that receive the beams of light reflected by the toner pattern. The lighting optical system has a lateral magnification m that satisfies mP/S, where S is the size of the light-emitting elements and P is the arrangement pitch of the light-emitting elements.

An image forming apparatus includes an image forming device, a print object moving device configured to move a print object in a moving direction relatively to the image forming device, a detector configured to detect images formed on the print object, and a control device configured to control the image forming device to form a first plurality of marks and a second plurality of marks on the print object. The first marks are along the moving direction and the second marks are along the moving direction and to be away from the first marks in a width direction that is perpendicular to the moving direction and the second marks are smaller in number than the first marks. The control device is further configured to control the detector to detect the first marks and the second marks on the print object for detecting deviation in image forming positions.

An image forming apparatus including: a first and a second photosensitive members, an endless transfer belt, a transfer unit configured form a transfer nip with the endless transfer belt, a storage unit configured to store first and second delay data each indicating an amount of delay of a second exposure start timing of the second photosensitive member with respect to a first exposure start timing of the first photosensitive member, a control unit configured to control the second exposure start timing based on the first delay data until a first recording medium enters the transfer nip and control the second exposure start timing based on the second delay data after the first recording medium enters the transfer nip.

An image forming apparatus includes an apparatus main body, a photoreceptor drum, a charging apparatus, an exposure apparatus, a developing device, a charging bias applying unit, a developing bias applying unit, an image condition adjusting unit, and a print density measurement unit. The image condition adjusting unit forms a second electric potential region by applying the charging bias where a first differential electric potential is subtracted from a first tentative charging bias on a circumference surface of a photoreceptor drum, and forms a second toner image by an electric potential difference between the second electric potential region and a developing roller by applying the target electric potential. The image condition adjusting unit decides value of the charging bias corresponding to the target electric potential from measurement results of print densities of a first toner image and the second toner image measured by the print density measurement unit.

An image forming apparatus includes a sheet transport path that transports a sheet on which an image has been recorded, the sheet transport path including a first guide surface and a second guide surface opposed to the first guide surface, an image reading unit disposed on the same side as the first guide surface of the sheet transport path to read the image, and a rotary element disposed on the same side as the second guide surface, the rotary element being rotatably disposed with a gap between the rotary element and the first guide surface.

An image forming apparatus forms test patches, and detects the adhesion amounts of toner in the test patches. The image forming apparatus calculates an approximate equation approximates the relationship between a developing bias and an adhesion amount of toner, based on the developing biases when the test patches were formed and the adhesion amounts of toner of the test patches. Distance between test patches is {(2n1)/2} times of value L, where n is a natural number and L is a length of the photo conductor drum in a circumferential direction. The accuracy of toner adhesion amount control can be improved, and image density can be stabilized.

An image forming apparatus includes an image forming unit, a human-body detection unit, an instruction receiver, and a controller. The controller determines whether an adjustment process is to be performed in accordance with a result of a determination, at an end of an image forming process, as to whether a human body is detected. The controller executes the adjustment process when the image forming process is terminated where the human-body detection unit does not detect a human body. The controller starts the image forming process before the adjustment process is executed where a human body is detected and the image forming instruction is received within a predetermined period. The controller executes the adjustment process when the predetermined period has elapsed while the image forming instruction is not received after the end of the image forming process where the human-body detection unit detects a human body.

An image forming apparatus determines, based on detection performed by an optical sensor unit on an intermediate transfer belt while light-emitting devices emit a predetermined amount of light, an amount of light the light-emitting devices emit when the optical sensor unit detects a misregistration detection toner pattern and a density variation detection toner pattern.

An image formation apparatus includes: image formation units mounted in series in a conveyance direction of a transfer object and that form images and correction patterns of different color developers on the transfer object; a sensor that detects a color misregistration, by the emission of a detection light to the correction pattern on the transfer object and the reception of a reflection light from the transfer object; an identification unit that identifies, out of the image formation units, a first image formation unit using a first developer which is the developer with the lowest reflectance, based on reflectance information indicating reflectances of the developers for the image formation units, or based on color information indicating the colors of the developers for the image formation units; and a corrector that corrects the color misregistration with respect to the first image formation unit identified by the identification unit.

An image forming apparatus includes a density adjusting unit that executes first formation of forming a first color sample in a transfer area on an image carrier, first adjustment of adjusting output characteristics of an image forming unit to reduce a difference between a measured density of the first color sample and a first target density, second formation of forming a second color sample in a non-transfer area on the image carrier, second adjustment of adjusting the output characteristics to reduce a difference between a measured density of the second color sample and a second target density, and third adjustment of adjusting the output characteristics to reduce a difference in output density between the transfer and non-transfer areas, if the difference between the measured density of the second color sample and the second target density exceeds a predetermined extent after repeating the second formation and the second adjustment.