Abstract: Non-contacting caliper measurements of free-standing sheets detect mid-IR interferometric fringes created by the reflection of light from the top and bottom surfaces of the sheet. The technique includes directing a laser beam at a selected angle of incidence onto a single spot on the exposed outer surface and scanning the laser beam through a selected wavelength range as the laser beam is directed onto the exposed outer surface and measuring the intensity of an interference pattern that forms from the superposition of radiation that is reflected from the exposed outer surface and from the inner surface. Alternatively, the intensity of an interference pattern formed from the superposition of radiation that is directly transmitted through the web and radiation that is transmitted through the web after internal reflections from the internal surfaces of the web. Thickness can be extracted from the fringe separation in the interference pattern.

Abstract: A method of level finding includes providing characteristics of a shape of a transmitted pulse in time domain launched onto a waveguide into a tank having at least one material therein, physical properties of the waveguide and real and imaginary dielectric characteristics of the material at a frequency of the pulse. A level finding algorithm having a coarse search and a fine search is implemented, where the coarse search minimizes a prediction error between an echo signal (echo curve y(k)) and a sampled pulse model echo p(k) to obtain an objective function J(k) in a vicinity of a minimum prediction error (k*). The fine search calculates at least one minimum or maximum using J(k) in the vicinity of k*. The minimum or the maximum corresponds to a level of the material or an interface involving the material.

Abstract: Non-contacting caliper measurements of free standing sheets such as porous polymer and paper detect mid-IR interferometric fringes created by the reflection of light from the top and bottom surfaces of the sheet. The technique includes directing a laser beam at a selected angle of incidence onto a single spot on the exposed outer surface wherein the laser beam comprises radiation having a wavelength in the 3-50 micron range and scanning the laser beam through a selected angle range as the laser beam is directed onto the exposed outer surface and measuring the intensity of an interference pattern that forms from the superposition of radiation that is reflected from the exposed outer surface and from the inner surface. Thickness can be extracted from the fringe separation in the interference pattern. Rotating and focusing elements ensure that the spot position on the sheet remains the same while varying the incident angle.

Abstract: A method of pulsed radar interface determination for a first and second material in a tank. An interface level determination model is provided including a transfer function that utilizes refractive indices for the materials and thickness of the second material. At least one actual radar pulse is transmitted into the tank and a resulting echo curve portion including a measured interface pulse(s) around the interface location is measured. The interface model is simulated with a reference pulse and an initial thickness value to generate an initial model generated interface pulse (initial MGIP). The measured interface pulse is compared to the initial MGIP pulse point-by-point to determine residuals. If the residuals sum >a predetermined threshold, the comparing is repeated with an updated interface model generated with an updated thickness value that provides an updated MGIP pulse. When the sum of residuals is ?predetermined threshold, the thickness is determined.

Abstract: A method of modeling a pulsed radar gauge (PRG) that includes a transceiver coupled by a process connection to a probe installed on a tank having at least one product material therein. A mathematical model is provided that includes (i) dielectric properties and dimensions of materials used in the process connection, (ii) at least one tank dimension, (iii) dielectric characteristics of the product material, and (iv) a probe length. Using a processor implementing a stored echo prediction algorithm that utilizes the mathematical model inputting pulse characteristics including a shape of an input radar pulse launched by a transmitter of the transceiver onto the probe into the mathematical model, and generating a predicted echo curve from the mathematical model.

Abstract: Non-contacting caliper measurements of free-standing sheets detect mid-IR interferometric fringes created by the reflection of light from the top and bottom surfaces of the sheet. The technique includes directing a laser beam at a selected angle of incidence onto a single spot on the exposed outer surface and scanning the laser beam through a selected wavelength range as the laser beam is directed onto the exposed outer surface and measuring the intensity of an interference pattern that forms from the superposition of radiation that is reflected from the exposed outer surface and from the inner surface. Alternatively, the intensity of an interference pattern formed from the superposition of radiation that is directly transmitted through the web and radiation that is transmitted through the web after internal reflections from the internal surfaces of the web. Thickness can be extracted from the fringe separation in the interference pattern.

Abstract: Non-contacting caliper measurements of free standing sheets such as porous polymer and paper detect mid-IR interferometric fringes created by the reflection of light from the top and bottom surfaces of the sheet. The technique includes directing a laser beam at a selected angle of incidence onto a single spot on the exposed outer surface wherein the laser beam comprises radiation having a wavelength in the 3-50 micron range and scanning the laser beam through a selected angle range as the laser beam is directed onto the exposed outer surface and measuring the intensity of an interference pattern that forms from the superposition of radiation that is reflected from the exposed outer surface and from the inner surface. Thickness can be extracted from the fringe separation in the interference pattern. Rotating and focusing elements ensure that the spot position on the sheet remains the same while varying the incident angle.

Abstract: Non-contacting caliper measurements of free standing sheets such as porous polymer and paper detect mid-IR interferometric fringes created by the reflection of light from the top and bottom surfaces of the sheet. The technique includes directing a laser beam at a selected angle of incidence onto a single spot on the exposed outer surface wherein the laser beam comprises radiation having a wavelength in the 3-50 micron range and scanning the laser beam through a selected angle range as the laser beam is directed onto the exposed outer surface and measuring the intensity of an interference pattern that forms from the superposition of radiation that is reflected From the exposed outer surface and from the inner surface. Thickness can be extracted from the fringe separation in the interference pattern. Rotating and focusing elements ensure that the spot position on the sheet remains the same while varying the incident angle.

Abstract: A method of pulsed radar interface determination for a first and second material in a tank. An interface level determination model is provided including a transfer function that utilizes refractive indices for the materials and thickness of the second material. At least one actual radar pulse is transmitted into the tank and a resulting echo curve portion including a measured interface pulse(s) around the interface location is measured. The interface model is simulated with a reference pulse and an initial thickness value to generate an initial model generated interface pulse (initial MGIP). The measured interface pulse is compared to the initial MGIP pulse point-by-point to determine residuals. If the residuals sum >a predetermined threshold, the comparing is repeated with an updated interface model generated with an updated thickness value that provides an updated MGIP pulse. When the sum of residuals is ?predetermined threshold, the thickness is determined.

Abstract: A method of modeling a pulsed radar gauge (PRG) that includes a transceiver coupled by a process connection to a probe installed on a tank having at least one product material therein. A mathematical model is provided that includes (i) dielectric properties and dimensions of materials used in the process connection, (ii) at least one tank dimension, (iii) dielectric characteristics of the product material, and (iv) a probe length. Using a processor implementing a stored echo prediction algorithm that utilizes the mathematical model inputting pulse characteristics including a shape of an input radar pulse launched by a transmitter of the transceiver onto the probe into the mathematical model, and generating a predicted echo curve from the mathematical model.

Abstract: A method of level finding includes providing characteristics of a shape of a transmitted pulse in time domain launched onto a waveguide into a tank having at least one material therein, physical properties of the waveguide and real and imaginary dielectric characteristics of the material at a frequency of the pulse. A level finding algorithm having a coarse search and a fine search is implemented, where the coarse search minimizes a prediction error between an echo signal (echo curve y(k)) and a sampled pulse model echo p(k) to obtain an objective function J(k) in a vicinity of a minimum prediction error (k*). The fine search calculates at least one minimum or maximum using J(k) in the vicinity of k*. The minimum or the maximum corresponds to a level of the material or an interface involving the material.

Abstract: Robust terahertz time-domain spectrometer has a reflective surface arrangement that renders the sensor insensitive to x or y displacement. The apparatus includes: (a) first scanner head; (b) a first reflective surface; (c) emitter; (d) beam splitter to yield reference radiation pulses and sample radiation pulses; (e) first reflector to reflect sample radiation pulses that have been transmitted through the sample to generate reflected sample radiation pulses that are directed towards a web; (f) second reflector that reflects the reference radiation pulses to generate reflected reference radiation pulses that are directed towards the beam splitter which in turn transmits a portion of the reflected references radiation pulses towards the web; and (g) a detector that receives (i) the reflected sample radiation pulses that have interacted with the sample a plurality of times and (ii) reflected reference radiation pulses that have interacted with the sample a plurality of times.

Abstract: Robust terahertz time-domain spectrometer has a reflective surface arrangement that renders the sensor insensitive to x or y displacement. The apparatus includes: (a) first scanner head; (b) a first reflective surface; (c) emitter; (d) beam splitter to yield reference radiation pulses and sample radiation pulses; (e) first reflector to reflect sample radiation pulses that have been transmitted through the sample to generate reflected sample radiation pulses that are directed towards a web; (f) second reflector that reflects the reference radiation pulses to generate reflected reference radiation pulses that are directed towards the beam splitter which in turn transmits a portion of the reflected references radiation pulses towards the web; and (g) a detector that receives (i) the reflected sample radiation pulses that have interacted with the sample a plurality of times and (ii) reflected reference radiation pulses that have interacted with the sample a plurality of times.

Abstract: An analytical model simulates the propagation of radiation through a coated continuous web where layer thickness and refractive index, as variables, determine the speed and direction of transmitted radiation. The model predicts characteristics of transmitted radiation based on characteristics of incident radiation and initially assigned values for layer thicknesses. Coating thickness(s) are ascertained in a process whereby incident radiation of known characteristics is directed onto a coated web and thereafter, actual measurements of transmitted radiation are compared to predicted characteristics. Using a fitting algorithm, the assigned thickness(es) of the layer(s) of the model are adjusted and the process repeated until the actual and predicted values are within desired limits at which time, the assigned thickness(es) represent the measured calipers.

Abstract: Non-contacting caliper measurements of free-standing sheets detect mid-IR interferometric fringes created by the reflection of light from the top and bottom surfaces of the sheet. The technique includes directing a laser beam at a selected angle of incidence onto a single spot on the exposed outer surface and scanning the laser beam through a selected wavelength range as the laser beam is directed onto the exposed outer surface and measuring the intensity of an interference pattern that forms from the superposition of radiation that is reflected from the exposed outer surface and from the inner surface. Alternatively, the intensity of an interference pattern formed from the superposition of radiation that is directly transmitted through the web and radiation that is transmitted through the web after internal reflections from the internal surfaces of the web. Thickness can be extracted from the fringe separation in the interference pattern.

Abstract: Non-contacting caliper measurements of free standing sheets such as porous polymer and paper detect mid-IR interferometric fringes created by the reflection of light from the top and bottom surfaces of the sheet. The technique includes directing a laser beam at a selected angle of incidence onto a single spot on the exposed outer surface wherein the laser beam comprises radiation having a wavelength in the 3-50 micron range and scanning the laser beam through a selected angle range as the laser beam is directed onto the exposed outer surface and measuring the intensity of an interference pattern that forms from the superposition of radiation that is reflected From the exposed outer surface and from the inner surface. Thickness can be extracted from the fringe separation in the interference pattern. Rotating and focusing elements ensure that the spot position on the sheet remains the same while varying the incident angle.

Abstract: An analytical model simulates the propagation of radiation through a coated continuous web where layer thickness and refractive index, as variables, determine the speed and direction of transmitted radiation. The model predicts characteristics of transmitted radiation based on characteristics of incident radiation and initially assigned values for layer thicknesses. Coating thickness(s) are ascertained in a process whereby incident radiation of known characteristics is directed onto a coated web and thereafter, actual measurements of transmitted radiation are compared to predicted characteristics. Using a fitting algorithm, the assigned thickness(es) of the layer(s) of the model are adjusted and the process repeated until the actual and predicted values are within desired limits at which time, the assigned thickness(es) represent the measured calipers.

Abstract: An apparatus for incorporation into time-domain spectroscopy systems that creates a continuous reference whereby a sample pulses' phase and amplitude can be tracked and corrected employs a beam splitter to generate sample and reference pulses. A detector is positioned for receiving the reference radiation pulses that do not interact with the sample. The same detector is also positioned for receiving the sample radiation pulses that emerge from the sample. The apparatus can be readily implemented by being configured between the emitter and detector of a terahertz time-domain spectrometer. The reference pulse is used to trace the changes in time and amplitude of the sample pulse. Since any changes in the reference pulse will most likely manifest in the sample pulse, the reference pulse is monitored and used to correct the sample pulse and thereby reduce the effects of jitter.

Abstract: An apparatus for incorporation into time-domain spectroscopy systems that creates a continuous reference whereby a sample pulses' phase and amplitude can be tracked and corrected employs a beam splitter to generate sample and reference pulses. A detector is positioned for receiving the reference radiation pulses that do not interact with the sample. The same detector is also positioned for receiving the sample radiation pulses that emerge from the sample. The apparatus can be readily implemented by being configured between the emitter and detector of a terahertz time-domain spectrometer. The reference pulse is used to trace the changes in time and amplitude of the sample pulse. Since any changes in the reference pulse will most likely manifest in the sample pulse, the reference pulse is monitored and used to correct the sample pulse and thereby reduce the effects of jitter.