An image forming apparatus includes a developing unit, a transfer unit, a power source unit configured to supply a developing bias voltage to the developing unit and a transfer bias voltage to the transfer unit, and an input device to receive an image density evaluation. A processor performs adjusts the developing bias voltage when an evaluation input indicating a defect in the image density is received. If, after the first adjustment, another evaluation input indicating a defect in image density is received, the processor adjusts one of the developing bias voltage, the transfer bias voltage, or the toner density in the developing unit.

An image forming apparatus includes: plural image forming units that each include plural image forming sections and a first intermediate transfer body to which toner images formed by the plural image forming sections are transferred through first transfer; plural second transfer sections provided in correspondence with the plural image forming units to transfer the toner images on the first intermediate transfer body to a recording medium through second transfer; and a detection device that detects the toner images downstream of a most downstream one of the second transfer sections.

An image forming apparatus includes a developing unit, a transfer unit, a power source unit configured to supply a developing bias voltage to the developing unit and a transfer bias voltage to the transfer unit, and an input device to receive an image density evaluation. A processor adjusts the developing bias voltage when an evaluation input indicating a defect in the image density is received. If, after the first adjustment, another evaluation input indicating a defect in image density is received, the processor adjusts one of the developing bias voltage, the transfer bias voltage, or the toner density in the developing unit.

An image forming apparatus includes a processor that derives, for each of a plurality of blocks of image data, a value indicating a toner amount to be used in forming a toner image by referring to a density of every pixel, of a plurality of pixels included in each block of image data, shifts a window, and outputs the window before shifting and the window after shifting, the window before shifting and the window after shifting overlapping with each other, and determines a fixing temperature for a fixing operation based on an analysis result of a first toner amount in the window that is output by referring to the toner amount of each block included in the window before shifting, and an analysis result of a second toner amount in the window that is output by referring to the toner amount of each block included in the window after shifting.

An optical sensor includes a first LED, a second LED, a first PD, and a second PD. The first LED and the second LED are configured to irradiate an optical-axis center point of an intermediate transfer belt. The first PD is arranged at a position at which specularly reflected light of light emitted from the first LED and diffused reflected light of light emitted from the second LED are received. The second PD is arranged at a position at which diffused reflected light of the light emitted from the first LED is received.

An image forming apparatus includes an optical sensor configured to detect an image formed on an intermediate transfer belt. The optical sensor includes a first LED, a second LED, a first PD, and a second PD. The first LED and the second LED irradiate an optical-axis center point of an intermediate transfer belt. The first PD is arranged at a position at which an optical axis of specularly reflected light of light emitted from the second LED and an optical axis along which specularly reflected light of light emitted from the first LED is received form an angle . The second PD is arranged at a position at which the optical axis of the specularly reflected light of the light emitted from the second LED and an optical axis along which diffused reflected light of the light emitted from the second LED is received.

An example shutter unit includes a motor including a driving shaft to rotate in a first rotation direction and to rotate in a second rotation direction opposed to the first rotation direction, a first shutter part to selectively expose a light window by receiving a driving force transferred from the driving shaft when the driving shaft rotates in the first rotation direction or the second rotation direction, and a second shutter part to selectively expose a sensor by receiving the driving force transferred from the driving shaft when the driving shaft rotates in the second rotation direction.

A downtime relating to formation and detection of a detection image is reduced. An image forming apparatus includes a controller configured to calculate a first conversion unit to convert a gradation of input image data so that density output for the input image data becomes a first density output characteristic based on a first detection result of the detection image detected by a density sensor in a first mode. The controller generates a second conversion unit to convert the gradation of the input image data so that the density output for the input image data becomes a second density output characteristic in a second mode based on the detection result in the first mode and correction information, and further updates the correction information based on a second detection result of the detection image detected by the density sensor in the second mode and the first detection result.

An image forming apparatus includes a sensor assembly having a window and a sensor which senses a developer through the window, and a shutter device which opens and closes the window, and thereby sensing in a sensible state is maintained, and a lifetime thereof is extendable.

An image forming apparatus includes first to third adjustment processing portions. The first adjustment processing portion adjusts an emission light amount of a light-emitting portion of a first sensor based on an electric signal output from a light-receiving portion of the first sensor and corresponding to regular reflection light reflected by a non-toner-adhering surface of an image-carrying member. The second adjustment processing portion adjusts an operation condition of an image forming portion based on a toner concentration of a first toner image in a specific color, that has a concentration smaller than a predetermined saturation concentration. The third adjustment processing portion adjusts an emission light amount of a light-emitting portion of a second sensor based on an electric signal output from a light-receiving portion of the second sensor and corresponding to diffuse reflection light reflected by a second toner image in the specific color, that has a predetermined reference concentration.