An embodiment provides an image forming apparatus that has a first operation mode and a second operation mode. The first operation mode forms an image on a sheet with toner. The second operation mode decolorizes the toner on the sheet on which the image is formed with a decolorable toner having a decoloring function. In the first operation mode, when the sheet passes through a transfer unit, a transfer bias having the same polarity as that of a charge of the toner is applied to the transfer member and a toner image formed on a surface of the transfer member is transferred to the sheet. In the second operation mode, when the sheet passes through the transfer unit, a cleaning bias having a reverse polarity to that of the transfer bias is applied to the transfer member.

In an image forming apparatus, a control unit performs a control for determining a surface potential A to determine a first voltage to be applied to a charge roller by a charge voltage application circuit so that a surface potential of a photosensitive drum becomes a first potential. The charge voltage application circuit thereafter applies the first voltage to the charge roller to charge the photosensitive drum. In such a state, the control unit performs a second control to determine a light amount of a laser light source, so that the surface potential of the photosensitive drum becomes a second potential. In such a manner, a potential of a photosensitive drum surface is detected with high accuracy. Moreover, a time taken to detect the potential of the photosensitive drum surface is shortened.

An image forming apparatus includes an image bearer, a nip former, a transfer bias supply, and processing circuitry. The nip former to form a transfer nip between the image bearer and the nip former. The transfer bias supply applies a transfer bias in which an alternating current component is superimposed on a direct current component to the transfer nip, to transfer a toner image onto a transfer target object at the transfer nip. The processing circuitry is to execute a processing mode of determining the DC component and the AC component to be used in a print job, based on a plurality of test toner images transferred to the transfer target object under transfer conditions different from each other in combination of the DC component and the AC component while changing the DC component and the AC component.

A method of controlling transfer power of an image forming apparatus includes: determining a sensing feedback voltage by applying a set sensing current and measuring a first output voltage during a time period before an image is transferred to a transfer medium; measuring humidity and comparing the measured humidity with a set value; setting a target voltage based on the determined sensing feedback voltage when the measured humidity is equal to or higher than the set value; and adjusting the transfer current to apply the target voltage during a time period in which the image is transferred to the transfer medium.

In one example, a method for calibrating a position of a charge roller is described. The method may include a processor positioning a first end of a charge roller to a first plurality of index positions, determining a capacitance between the charge roller and a photoconductor imaging plate at each of the first plurality of index positions, determining a first index position of the first plurality of index positions with a greatest change in capacitance, and calibrating a position of the charge roller based upon the first index position.

An image forming system includes an image holding unit that is rotatably provided and that holds an image formed by means of a charged image forming material, a transfer unit that transfers the image hold by the image holding unit to a medium by using a transfer electric field, a fine particle applying unit that periodically or irregularly applies lubricant fine particles to the image holding unit, and a transfer control unit that controls the transfer electric field of the transfer unit depending on a state of application of the fine particles on the image holding unit.

An image forming apparatus includes the following elements. Plural developing units supply charged developers to electrostatic latent images formed on plural associated image carriers disposed along a direction in which an intermediate transfer body is transported. Plural first transfer units transfer the associated developers onto the intermediate transfer body when the intermediate transfer body passes the associated image carriers while being transported so as to superpose the developers on each other. A second transfer unit transfers the superposed developers transferred onto the intermediate transfer body by the plural first transfer units onto a recording medium. A charge-amount adjusting unit decreases an amount of electric charge of a developer which forms a lower layer developer among the superposed developers transferred onto the intermediate transfer body. A brightness level of the lower layer developer is lower than that of a developer which forms an upper layer developer among the superposed developers.

In an example, a method of controlling voltage applied to a print blanket within a printing device includes printing a print job. During the printing, a null cycle trigger is received. In response to the trigger, a print blanket bias voltage is reduced from a print bias level to a null bias level.

An image forming apparatus is provided that includes a light-emitting unit which emits light to an image bearing member which bears a developer image and that detects presence or absence of a developer container storing developer or a shape of the developer container on the basis of the number of electrons discharged from or received by the image bearing member when the light-emitting unit emits the light.

An image forming apparatus includes a plurality of image carriers, a charging device, an exposure device, a development device, and an intermediate transfer belt. The image carrier has a surface on which an amorphous silicon photosensitive layer is formed. The intermediate transfer belt is a plastic belt having a surface resistivity of 9.5 to 10.5 (log /square). An offset amount of the primary transfer roller from the image carrier is 0 to 2 (mm), a contact surface pressure between the image carrier and the intermediate transfer belt is 0.5 to 1.5 (gf/mm.sup.2), and a charge density of primary transfer current that flows when the primary transfer voltage is applied to the primary transfer roller is 0.016 to 0.040 (C/cm.sup.2).