A moisture detecting apparatus includes: a light emitting unit including a first light source configured to emit light having a first wavelength as a peak wavelength, and a second light source configured to emit light having a second wavelength as a peak wavelength; a detecting unit configured to detect a first detection value indicating an extent to which the light emitted from the first light source is transmitted through a recording material, and a second detection value indicating an extent to which the light emitted by the second light source is transmitted through the recording material, based on a light receiving result of a light receiving unit; and a determination unit configured to determine a value related to a moisture content of the recording material based on the first detection value and the second detection value.

A moisture detecting apparatus includes: a light emitting unit including a first light source configured to emit light having a first wavelength as a peak wavelength, and a second light source configured to emit light having a second wavelength as a peak wavelength; a detecting unit configured to detect a first detection value indicating an extent to which the light emitted from the first light source is transmitted through a recording material, and a second detection value indicating an extent to which the light emitted by the second light source is transmitted through the recording material, based on a light receiving result of a light receiving unit; and a determination unit configured to determine a value related to a moisture content of the recording material based on the first detection value and the second detection value.

A signal detection device according to one aspect of the present invention includes a receiver configured to receive a signal including at least a first signal component modulated by a first frequency and a second signal component modulated by a second frequency, and a detector configured to generate, using a base signal, a first reference signal to be used for detecting the first signal component and a second reference signal to be used for detecting the second signal component, perform lock-in detection on the signal received by the receiver using the first reference signal to obtain a first detection signal, perform lock-in detection on the signal received by the receiver using the second reference signal to obtain two second detection signals having different phases from each other, and change at least one of a frequency and a phase of each of the first and second reference signals to set one of the two second detection signals to zero.

A signal detection device according to one aspect of the present invention includes a receiver configured to receive a signal including at least a first signal component modulated by a first frequency and a second signal component modulated by a second frequency, and a detector configured to generate, using a base signal, a first reference signal to be used for detecting the first signal component and a second reference signal to be used for detecting the second signal component, perform lock-in detection on the signal received by the receiver using the first reference signal to obtain a first detection signal, perform lock-in detection on the signal received by the receiver using the second reference signal to obtain two second detection signals having different phases from each other, and change at least one of a frequency and a phase of each of the first and second reference signals to set one of the two second detection signals to zero.

Continuous on-line thin film measurements employ a sensor having a spectrometer for interferometric measurements and a stack of single channel detectors for adsorption measurements. The stack is separated from the spectrometer, which analyzes radiation that emerges (transmitted pass or reflected from) the film, whereas the stack analyzes radiation that has passed through the film multiple times. The spectrometer is (i) positioned directly opposite the source of radiation so that it detects transmitted radiation or (ii) disposed on the same side of the film as is the source of radiation so that the spectrometer detects radiation that is specularly reflected from the film. The sensor includes a broadband radiation source emitting visible to far infrared light which propagates through a measurement cell defined by reflective surfaces exhibiting Lambertian-type scattering. The sensor is capable of measuring thin plastic films with thicknesses down to 1 micron or less.

Near infrared moisture sensors using stable holmium oxide glass calibration standards that simulate different moistures levels in paper obviates problems associated with glass encased paper samples. Holmium oxide glass has a strong absorption at 1.93 microns which is close to absorption by paper. Standards can have varying thicknesses to simulate different moisture levels. Didymium glass can also be used with holmium oxide glass. The moisture sensor operates at reference and measurement infrared regions of 1.94 microns and 1.8 microns, respectively.

Near infrared moisture sensors using stable holmium oxide glass calibration standards that simulate different moistures levels in paper obviates problems associated with glass encased paper samples. Holmium oxide glass has a strong absorption at 1.93 microns which is close to absorption by paper. Standards can have varying thicknesses to simulate different moisture levels. Didymium glass can also be used with holmium oxide glass. The moisture sensor operates at reference and measurement infrared regions of 1.94 microns and 1.8 microns, respectively.

A method of calculating a first parameter of a first sample of a material is provided. The method includes determining a first and second wavelengths at which the material exhibits substantially no absorption; measuring a transmission of the first sample at the first wavelength; measuring a transmission of the first sample at the second wavelength; and calculating the first parameter of the first sample using a first multivariate regression model including first regression coefficients. The first parameter is a parameter which affects a total amount of radiation scattered by the first sample at the first and second wavelengths.

Optical multi-channel measurement unit for a process measurement includes first ends for receiving optical radiation from the optical radiation source, and second ends for outputting the optical radiation for illuminating the at least one object. Optical detectors receive optical radiation from at least one measurement channel via at least one optical filter and convert an intensity of the optical radiation to an electrical signal. A movement mechanism causes, for filtering the wavelengths of the optical radiation propagating between detectors and the optical measurement channels through the optical filters, at least one of the following: movement inside at least one optical filter and movement between the filters and the detectors.

Optical multi-channel measurement unit for a process measurement includes first ends for receiving optical radiation from the optical radiation source, and second ends for outputting the optical radiation for illuminating the at least one object. Optical detectors receive optical radiation from at least one measurement channel via at least one optical filter and convert an intensity of the optical radiation to an electrical signal. A movement mechanism causes, for filtering the wavelengths of the optical radiation propagating between detectors and the optical measurement channels through the optical filters, at least one of the following: movement inside at least one optical filter and movement between the filters and the detectors.