An image forming apparatus includes an apparatus body, an image bearing member, and a process unit attached to the apparatus body. The process unit includes a frame including a storage portion configured to store developer, a developer bearing member configured to supply developer to the image bearing member to develop an electrostatic latent image. and a circuit board attached to the frame. The circuit board includes a light emitting portion configured to emit light, and a light receiving portion configured to receive the light emitted from the light emitting portion and having passed through an interior of the storage portion.

An image forming apparatus includes a developing section, storage, a first calculation section, a comparing section, and an executing section. The developing section develops an electrostatic latent image with toner. The storage stores coverage rates. The first calculation section calculates a first coverage rate and a second coverage rate. The comparing section compares the first coverage rate with the second coverage rate. The first coverage rate includes one or more coverage rates stored earlier in the storage than the second coverage rate. The second coverage rate includes coverage rates of a specified number of latest images individually formed on a specified number of sheets. A running-in operation is driving the developing section. The executing section executes the running-in operation.

A sensor unit detachably mounted in a main assembly of an image forming apparatus includes a sensor for detecting a detection object on a surface of a movable member, the sensor having a detecting surface positioned to face the surface of the movable member at least when the sensor detects the detection object; a casing portion accommodating the sensor; an air feeding unit, provided in the casing portion, for taking air in through an inlet portion formed by the casing; and a duct for feeding the air discharged from the air feeding unit to a space between the detecting surface and the surface of the movable member.

An image forming apparatus includes a latent image forming portion configured to form a latent image on an image bearing member; a developing device including a container configured to store toner and a developing member configured to supply the toner to the latent image formed on the image bearing member to form a toner image; an environment sensor configured to detect environmental information related to an environment in which the developing device is placed; and a controller configured to control switching between a first mode and a second mode, in which a number of prints per unit time is less than that in the first mode. The controller is configured to perform switching from the first mode to the second mode based on an update value obtained by adding or subtracting over time an index value weighted in accordance with the environmental information detected by the environment sensor.

An evaluation device evaluates an image clarity of a print image. The evaluation device includes: an object that is projected onto a measurement surface of a recording medium; an illuminator that makes the object projected onto the measurement surface; an imager that images the measurement surface on which the object has been projected to obtain image data; and a hardware processor that, based on a distribution of parameters related to a brightness of the image data, quantifies a degree of the image clarity into a numerical value and defines the numerical value as an evaluation value of the image clarity.

An image forming apparatus includes a developer case and a developer detection sensor. The developer detection sensor is disposed in contact with a contacted portion located near the developer in the developer case, and detects magnetic permeability of the developer. The developer detection sensor includes a substrate and one or more contact portions that are formed a facing region on a first surface of the substrate that faces the contacted portion, and configured to come in contact with the contacted portion. A first contact portion that is one of the contact portions includes a detection portion that detects magnetism of the developer. The detection portion is formed in a spiral shape extending from its center part outward. A first magnetic member is provided on the first surface, or on both the first surface and a second surface opposite from the first surface, at a position corresponding to the center part.

According to one embodiment, an image forming apparatus includes a developing device, a temperature sensor, and a controller. The developing device includes a developing roller configured to develop an electrostatic latent image with a toner and is supplied with the toner from at least one toner cartridge having a storage medium configured to store temperature information regarding melting of a contained toner. The temperature sensor detects the ambient temperature of the atmosphere including the developing device. The controller is configured to drive the developing roller of the developing device based on the ambient temperature detected by the temperature sensor and the temperature information stored in the storage medium.

An image forming apparatus includes a notification portion configured to notify replenishment information for prompting replenishing a developing container with developer in a case where an index is equal to or larger than a preset threshold value. The index is set such that the index increases in accordance with rotation of the developer bearing member and decreases in accordance with replenishment of the developing container with the developer. An amount of increase of the index per predetermined amount of rotation of the developer bearing member is larger in a case where an amount of the developer in the developing container is smaller. An amount of decrease of the index according to the replenishment of the developing container with the developer is larger in a case where an amount of replenished developer is larger.

An image forming apparatus includes an image bearing member, a rotatable developer carrying member, a rotatable toner supplying member, and a toner accommodating unit. A developing unit including the developer carrying member and the toner accommodating unit are capable of being independently exchanged. The image forming apparatus further includes a current detector and a controller configured to execute a process for notifying information on a lifetime of the developing unit, on the basis of a detection result of the current detector at predetermined timing after use of a fresh toner accommodating unit is started.

An image forming apparatus includes an image forming unit configured to form an image, a reader having a transparent member, the reader being configured to read an original through intermediation of the transparent member, a document feeder configured to feed the original in order to read the original by the reader, a reader image processor, and a controller. The controller is configured to control the image forming unit to form a test chart on a sheet, to control the reader image processor to detect the dust on the transparent member based on a result of reading the test chart, and to generate a conversion condition based on other signal values excluding an abnormal signal value caused by the dust on the transparent member.