An optical sensor of the present disclosure detects light reflected by a transported sheet and/or light transmitted through the sheet as well as light emitted from the sheet. The optical sensor includes: a light source configured to irradiate a sheet with excitation light and detection light; a controller configured to keep the light source turned off during each of light-off periods after the emission of the excitation light; and a light receiver configured to receive light resulting from reflection of the detection light by a sheet and/or light resulting from transmission of the detection light through the sheet in each of the light-on periods and receive phosphorescence emitted from the sheet in each of the light-off periods. The controller is configured to generate data of one pixel by summing up output values based on respective phosphorescence components received by the light receiver in each of the light-off periods.

An optical sensor of the present disclosure detects light reflected by a transported sheet and/or light transmitted through the sheet as well as light emitted from the sheet. The optical sensor includes: a light source configured to irradiate a sheet with excitation light and detection light; a controller configured to keep the light source turned off during each of light-off periods after the emission of the excitation light; and a light receiver configured to receive light resulting from reflection of the detection light by a sheet and/or light resulting from transmission of the detection light through the sheet in each of the light-on periods and receive phosphorescence emitted from the sheet in each of the light-off periods. The controller is configured to generate data of one pixel by summing up output values based on respective phosphorescence components received by the light receiver in each of the light-off periods.

A measurement device includes: a first measurement unit, disposed at a first opposing position facing a portion of a sheet-like measurement target, that measures a first physical property of the measurement target by causing the measurement target to vibrate with an ultrasonic wave; a second measurement unit, disposed at a second opposing position facing another portion of the measurement target in a state in which the first measurement unit is facing the first portion, that pinches and restrains the other portion in a thickness direction and measures a second physical property other than the first physical property of the measurement target; and a disposed unit disposed between the first measurement unit and the second measurement unit in an intersecting direction with respect to the thickness direction of the measurement target.

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.

A device for determining a layer thickness in a multilayer film includes a radiation source configured to generate an electromagnetic primary radiation, a detector configured to detect an electromagnetic secondary radiation emitted by the multilayer film, the secondary radiation being induced by an interaction of the primary radiation with the multilayer film, and a first contact block transparent to the electromagnetic primary radiation and having a first contact surface for creating contact with the multilayer film. The radiation source is arranged on the first contact block in such a way that the electromagnetic primary radiation is guided from the first contact block onto the multilayer film.

A device for determining a layer thickness in a multilayer film includes a radiation source configured to generate an electromagnetic primary radiation, a detector configured to detect an electromagnetic secondary radiation emitted by the multilayer film, the secondary radiation being induced by an interaction of the primary radiation with the multilayer film, and a first contact block transparent to the electromagnetic primary radiation and having a first contact surface for creating contact with the multilayer film. The radiation source is arranged on the first contact block in such a way that the electromagnetic primary radiation is guided from the first contact block onto the multilayer film.

A flexural-rigidity measuring apparatus includes an ultrasonic device including an oscillating unit that oscillates an ultrasonic wave toward a sheet and a receiving unit that receives the ultrasonic wave that has passed through the sheet, an electromagnetic induction device including an electromagnetic induction unit that generates electromagnetic induction with respect to a sheet, and a near-infrared spectroscopic device including a light-emitting unit that emits near-infrared light toward a sheet and a light-receiving unit that receives the near-infrared light that has passed through the sheet.

An apparatus and an associated method determine the fiber orientation of a moving fibrous web, in particular a paper, cardboard or cellulose web. An illumination device illuminates an area of the fibrous web and a camera records a digital image of the illuminated area of the fibrous web. The illumination device is configured to illuminate the fibrous web for a period of time of 1 μs or less and the camera is configured in such a way that the edge length of a pixel corresponds to no more than 20 μm, in particular no more than 10 μm.

An apparatus and an associated method determine the fiber orientation of a moving fibrous web, in particular a paper, cardboard or cellulose web. An illumination device illuminates an area of the fibrous web and a camera records a digital image of the illuminated area of the fibrous web. The illumination device is configured to illuminate the fibrous web for a period of time of 1 μs or less and the camera is configured in such a way that the edge length of a pixel corresponds to no more than 20 μm, in particular no more than 10 μm.

An image forming apparatus includes a detection sensor to irradiate light to a recording medium passing through a printing path, and detect an amount of light, a driving device to move a cleaning member to a cleaning region overlapping the printing path to clean a light window of the detection sensor, and a processor to confirm a position of the cleaning member based on the amount of light detected by the detection sensor and control the driving device to move the cleaning member based on the confirmed position.