An image forming apparatus including an image forming device, a sensor, and a processor. The image forming device is to form an image on recording medium. The sensor is to irradiate light to the recording medium and detect an amount of light transmitted through the recording medium and an amount of light reflected from the recording medium at each of a plurality of positions. The processor is to determine a thickness of the recording medium based on the amount of light transmitted through the recording medium and the amount of light reflected from the recording medium at each of the plurality of positions. The processor is to then control the image forming device on the basis of the determined thickness.

An image forming apparatus forms an image on a sheet and conveys the sheet through a conveying path. The image forming apparatus comprises a color detection sensor which detects a detection image formed on the sheet for generating an image forming condition and a white reference plate used to calibrate the color detection sensor. The white reference plate is arranged opposite to the color detection sensor interposing the conveying path therebetween at a position where the white reference plate is not concealed by the sheet when viewing from the color detection sensor when the sheet is conveyed to the conveying path. The detection image is formed on a white reference plate side of the sheet. The color detection sensor reads the white reference plate and is calibrated according to a read result.

An image formation system includes: a hardware processor that forms an image on a sheet based on a printing job, reads an output image formed on the sheet, assesses a quality of the output image based on the read output image, executes an invalid sheet process when an abnormal image is detected, interrupts the printing job when a time-over has occurred after executing the invalid sheet process; and restarts the printing job after inserting a divider sheet that indicates an occurrence of the time-over. The time-over occurs when quality assessment of the output image is completed outside of a predetermined time.

An image forming apparatus comprises a first conveyance unit, an image forming unit, a second conveyance unit, a stacking unit, and a control unit. The control unit controls, in a case where a sheet stacking condition of the stacking unit does not satisfy a predetermined stacking condition, the second conveyance unit to convey the sheet at a second conveyance speed that is faster than the first conveyance speed. The control unit controls, in a case where the sheet stacking condition of the stacking unit satisfies the predetermined stacking condition, the second conveyance unit to convey the sheet at a third conveyance speed that is slower than the second conveyance speed.

A recording material characteristic detecting device that irradiates a first light and a second light to a recording material carried along a predetermined carrying path and detects a transmitted light generated when the first light transmits the recording material and a reflection light generated when the second light is reflected by the recording material, and detects a characteristic of the recording material, comprises: a reflection light source that irradiates the second light toward the carrying path; a reference plate for reflection light arranged oppositely to the reflection light source across the carrying path to reflect the second light; and a light detector arranged oppositely to the reference plate for reflection light across the carrying path to detect at least a reflection light generated in response to reflection of the second light. The reference plate has a higher reflectivity to the second light than a reflectivity to the first light.

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.

In an image forming apparatus, a transfer material transport guide is disposed in an optical sensor unit to support a color deviation sensor, which is disposed near an intermediate transfer belt. By changing the position of the optical sensor unit, the grounding path of the transfer material transport guide can be changed, and both transfer bias leak prevention for the transfer material transport guide and electrostatic breakdown prevention for the color deviation sensor can be implemented. As a result, the apparatus can be downsized, and when the intermediate transfer belt is replaced, the optical sensor unit can be moved to create a space necessary for the replacement.

An image forming apparatus includes a memory and a controller. The memory is configured to store information related to a recording medium type detected by a detector in the past. The controller is configured to control a feeder so as to prevent feeding of a recording medium from starting, when a printing operation is started in a first mode, in a case that a recording medium type set through a setting unit and a recording medium type discriminated based on the information stored in the memory do not match with each other.

A recording medium determination device includes a light emitter, a light detector, and a hardware processor. The light emitter emits inspection light to a recording medium. The light detector detects incident light including at least one of diffuse reflected light of the inspection light emitted to the recording medium and fluorescent light excited by the inspection light in the recording medium. The hardware processor makes a determination depending on a property of the recording medium based on a detection result of first incident light of the incident light in accordance with first inspection light of the inspection light and second incident light of the incident light in accordance with second inspection light of the inspection light obtained by the light detector. The second inspection light has an intensity whose peak wavelength is shorter than the peak wavelength of the first inspection light.