Sensor and methods for measuring select components in sheetmaking systems

A sensor, for measuring at least one selected component in a composition, that comprises:

• (a) a broadband light source that generates light that is directed to the composition;
• (b) an acousto-optic tunable filter (AOTF) positioned to receive light that emerges from the composition wherein the AOTF is tuned to pass detected light having a desired wavelength range to detect the concentration of the at least one component in the composition;
• (c) detection means for receiving the detected light;
• and
• (d) a program structure that is coupled to the AOTF, the program structure capable of providing the AOTF with at least one desired wavelength range that is characteristic of the least one component in the composition.

A method for measuring the amount of at least one select component of a composition that comprises the steps of:

• (a) directing broadband light to an acousto-optic tunable filter (AOTF);
• (b) tuning the AOTE to pass a first detection light having a desired wavelength to detect the concentration of the a first component in the composition;
• (c) directing the first detection light to the composition;
• (d) detecting the intensity of the first detection light that emerges from the composition;
• (e) tuning the AOTF to change the wavelength of the detection light to generate a second detection light to measure a second component in the composition;
• (f) directing the second detection light to the composition;
• (g) detecting the intensity of the second detection light that emerges from the composition;
• (h) optionally, repeating steps (f) and (g) but for different wavelengths in order to measure one or more components other than the first and second components;
• and
• i optionally, measuring the temperature of the composition and changing the wavelength first or second detection light to optimize the intensity of the detection light that is measured.

A method for measuring the amount of at least one select component of a composition that comprises the steps of:

• (a) directing broadband light to the composition;
• (b) directing light that emerges from the composition into an acousto-optic tunable filter (AOTF);
• (c) tuning the AOTF to pass a first detection light having a desired wavelength to detect the presence of the a first component in the composition;
• (d) detecting the intensity of the first detection light that emerges from the composition;
• (e) tuning the AOTF to change the wavelength of the detection light to generate a second detection light to measure a second component in the composition;
• (f) detecting the intensity of the second detection light that emerges from the composition;
• (g) optionally, repeating steps (e) and (f) but for different wavelengths in order to measure one or more components other than the first and second components;
• and
• (h) optionally, measuring the temperature of the composition and changing the wavelength first or second detection light to optimize the intensity of the detection light that is measured.

A sensor, for measuring the thickness of an optically transparent film, thhat comprises:

• (a) a broadband light source;
• (b) an acousto-optic tunable filter (AOTF);
• (c) means for generating a beam of light from the light source and directing the beam of light at the AOTF wherein the AOTF is dynamically tuned over a range of wavelengths that can produce interference in the transparent film;
• (d) means for directing a collimated detection light of known wavelength to the film;
• (e) detection means for receiving light that emerges from the film;
• and
• (f) a program structure that is coupled to the AOTF, the program structure capable of providing the AOTF with at least one desired wavelength range that is capable of producing interference in the transparent film.

A sensor, for measuring the thickness of an optically transparent film, that comprises:

• (a) a broadband light source that generates light that is directed to the film;
• (b) an acousto-optic tunable filter (AOTF) positioned to receive light that emerges from the film wherein the AOTF is dynamically tuned over a range of wavelengths that can produce interference in the transparent film;
• (c) detection means for receiving a collimated detected light;
• and
• (d) a program structure that is coupled to the AOTF, the program structure capable of providing the AOTF with at least one desired wavelength range that is capable of producing interference in the transparent film.

A method for measuring the thickness of an optically transparent film that comprises the steps of:

• (a) directing broadband light to an acousto-optic tunable filter (AOTF);
• (b) dynamically tuning the AOTF to pass a first detection light having a desired swept wavelength band to produce interference in the optically transparent film;
• (c) directing the first detection light to the film;
• (d) detecting the intensity of the first detection light that emerges from the film;
• (e) detecting the change in intensity of the first detection light as the interference condition for the thickness of the optically transparent film is achieved;
• and
• (f) calculating the film thickness using the wavelength that produced the interference condition.

A method for measuring the thickness of an optically transparent film that comprises the steps of:

• (a) directing broadband light to the film;
• (b) directing light that emerges from the film into an acousto-optic tunable filter (AOTF);
• (c) dynamically tuning the AOTF to pass a first detection light having a desired swept wavelength band to produce interference in the optically transparent film;
• (d) detecting the intensity of the first detection light that emerges from the film;
• (e) detecting the change in intensity of the first detection light as the interference condition for the thickness of the optically transparent film is achieved;
• and
• (f) calculating the film thickness using the wavelength that produced the interference condition.