An image forming unit of an image forming apparatus includes a developing device and a toner replenishing unit that replenishes the developing device with toner. The toner replenishing unit includes an upper toner container, a lower toner container, a toner conveyance unit. The upper toner container and the lower toner container are disposed in a staggered manner in an apparatus body.

An image forming apparatus that performs primary transfer of single-color toner image onto an intermediate transfer belt and performs secondary transfer of the toner image onto a sheet, and includes: single image forming unit forming the single-color toner image; single toner supply bottle containing replenishment toner; and first and second support members supporting the belt. The image forming unit is closer to the first member than the second member in a belt rotation direction. The bottle includes: single bottle body; and supply unit near one end of the body in the rotation direction. The other end is (i) closer to the second member than the one end is in the rotation direction and (ii) distant from the image forming unit in a support member direction from the first member toward the second member by one to three times a length of the image forming unit in the support member direction.

An image forming apparatus, having first, second, and third photosensitive drums, a first developing cartridge including a first developing roller, a second developing cartridge including a second developing roller, a third developing cartridge including a third developing roller, an exposure device, a conveyer, and a moving mechanism, is provided. The first developing roller, the second developing roller, and the third developing roller are arranged in the recited order from upstream to downstream in a moving direction for the sheet to be conveyed. When the second developing roller is at the separated position thereof, the second developing cartridge coincides with a light path of the laser beam for scanning the first photosensitive drum. When the third developing roller is at the separated position thereof, the third developing cartridge coincides with a light path of the laser beam for scanning the second photosensitive drum.

An image forming apparatus, having first, second, and third photosensitive drums, a first developing cartridge including a first developing roller, a second developing cartridge including a second developing roller, a third developing cartridge including a third developing roller, an exposure device, a conveyer, and a moving mechanism, is provided. The first developing roller, the second developing roller, and the third developing roller are arranged in the recited order from upstream to downstream in a moving direction for the sheet to be conveyed. When the second developing roller is at the separated position thereof, the second developing cartridge coincides with a light path of the laser beam for scanning the first photosensitive drum. When the third developing roller is at the separated position thereof, the third developing cartridge coincides with a light path of the laser beam for scanning the second photosensitive drum.

An image forming apparatus includes an image forming unit that has multiple developing units, arranged in series for basic colors in a rotational driving direction of a transfer body, for developing toner images of the basic colors based on input image data and forms the overlapped toner images on a surface of the transfer body in a state in which the toner images are aligned; a transferring unit that transfers the toner images onto a sheet; and a controller that calculates a difference between color information of an image obtained by reading the toner images and color information of the input image data, calculates a color change direction of the toner images with respect to a color of the input image data based on the difference, and refers to a table and determines a shape of a surface of the sheet based on information of the color change direction.

An object of the present invention is to provide an image processing apparatus capable of reducing color material consumption to the maximum while maintaining the hue of an image before and after color conversion to reduce the color material consumption. The present invention is an image processing apparatus having a first lookup table to convert pixel values in a color space into pixel values of color materials, the apparatus including: an acceptable color difference derivation unit configured to derive an acceptable color difference indicating a size of a range of acceptable color difference, which corresponds to each grid point in the color space; a pixel value determination unit configured to determine pixel values of color materials, which corresponds to each of the grid points, based on the derived acceptable color difference; and a lookup table creation unit configured to create a second lookup table to convert pixel values in the color space into the determined pixel values of color materials.

An imaging device prints in color and monochromatically, such as black-only. It has a plurality of photoconductive drums, one each for black toner and at least one colored toner. The drums contact and rotate with an intermediate transfer member (ITM) to transfer images at a first transfer. During black-only imaging, the photoconductive drum for the black toner rotates with the ITM at process speed while the drum for the at least one colored toner rotates at less than process speed, often substantially less. The technique reduces consumption of colored toner during black-only imaging and minimizes charge build-up on the drum for the colored toner.

A color imaging device includes a plurality of developer rolls with a common operating point, such as a common operating voltage. To determine the operating point, an acceptable range of color density is determined for each toner, the range being lighter and darker than an optimum color density for that toner. A search range is devised such that values within the range are examined relative to deviations from the optimum color density per each toner. The common operating point is selected as that having the lowest deviation per all toners. Also, if the common operating point corresponds to a color density darker than the acceptable range of color density for any toner, additional halftoning occurs compared to traditional halftoning, such as for continuous tones or solids. In this way, four color developer rolls can be operated from a single power supply, yet still provide acceptable color images.

An image forming apparatus executes reverse charging, toner-supply suspension, second exposure, and second charging, while a photosensitive member rotates at least a full turn. In the reverse charging, a charger charges a portion of a circumferential surface of the photosensitive member to a specified polarity. In the toner-supply suspension, before the portion, which has been charged to the second polarity in the reverse charging, of the circumferential surface of the photosensitive member passes a position at which the developer from the developing unit is configured to initially adhered to the circumferential surface, a developing unit stops supplying developer to the circumferential surface. In the second exposure, an exposure device exposes the portion, which has been charged to the specified polarity in the reverse charging, of the circumferential surface. In the second charging the charger charges the portion, which has been exposed in the second exposure, of the circumferential surface.

A toner container used in an image forming apparatus including an exposure unit with a light emitting diode light source includes a container body, and a cyan toner stored in the container body. A lightness L*, a hue a*, and a hue b* of the cyan toner in a powder state satisfy

26.94L*34.84,

5.13a*3.83, and

47.47b*36.78.