Abstract: A flame detector unit contains a silicon photodiode that is sensitive to UV light waves and two lead selenide photoresistors that are sensitive to IR light waves. The electromagnetic bandwidth of each sensor element is restricted by an optical wave filter to pass photons of certain wavelengths characteristic of hydrocarbon flames and to discriminate against photons of other wavelengths. Signals generated by the IR sensors are in the form of variations in electrical resistance of the sensor elements, which together with a resistor network comprise a bridge circuit which combines the two IR signals so as to discriminate against blackbody radiation sources and provide a signal which is fed through an amplifier. Amplified UV and IR signals are fed to a common analog to digital converter (ADC). Output from the ADC is fed to a digital processor through a notch filter, a cluster of weighted-moving-average filters, and into a threshold comparator/tester.

Abstract: To measure water vapor and carbon dioxide, a gas analyzer includes a light source, a reference flow cell, a sample flow cell, and a detector. The light source, flow cells and detector are arranged so that the detector detects light transmitted from said light source through said reference flow cell and through said sample flow cell and generates a reference signal representing the light transmitted through a reference gas in said reference flow cell and a sample signal representing the light transmitted through a sample gas in said sample flow cell. The reference signal is subtracted from the sample signal to obtain an independant variable. A signal representing gross concentration of the carbon dioxide as a dependant variable is obtained from said independent variable from a stored empirically determined third power polynomial. The polynomial includes terms having at least first, second and third powers of said independant variable.

Abstract: The monitoring of energy radiating from a heated material, such as a hot melt adhesive, dispensed onto a substrate may be accomplished by an infrared sensor. The wand of the infrared sensor is located downstream of the dispensed material for receiving the radiant energy. The wand is provided with internal air for cooling and for providing laminar air flow in the vicinity of the lens to prevent the accumulation of airborne contaminants on the lens. The wand is also provided with a light aiming device.

Abstract: A method and apparatus to produce correction-free pyrometry is described. The method determines the optimum position for a pyrometer that "views" a specular, spherical or near-spherical target in a furnace through pyrometer optics and a window in a wall of the furnace. The positioning method uses nonparaxial optical analysis to determine the position of an image of the window in the target. The window image is free of any image of the furnace walls, that is, it is free from wall radiance, and pure target radiance can be obtained in that region. The optical analysis is then used to back project the pyrometer detector through the pyrometer optics and onto the surface of the target. If the detector projection falls completely within the image of the window, the detector will read only pure target radiance and no correction will be necessary to obtain the temperature of the target through pyrometry.

Abstract: The present invention relates to an apparatus and method of determining particulate integrated properties consisting of integrated volume concentration, integrated surface area concentration and aerosol extinction coefficient in the infrared portion of the light spectrum using a noncollimated light beam irradiating suspended particulates. A light trap is placed in front of the lens that collects the light scattered by the particulates. Two separate detectors are placed differently with respect to the noncollimated beam to measure the light scattered by the particulates. Variable transmission filters are placed in front of the detectors to correct for the distortions in the light scattered by the particulates due to the off-axis intensity of the noncollimated beam.

Abstract: A sheet break detector apparatus is disclosed for detecting a break in a sheet disposed contiguously between an upstream and a downstream felt of a paper machine dryer section. The detector apparatus includes an infrared light emitter disposed adjacent to the sheet disposed between the felts for emitting a beam of infrared light towards the sheet moving contiguously between the felts. An infrared light receiver is disposed on an opposite side of the felts relative to the emitter for receiving the beam in the absence of the sheet, the beam being blocked by the presence of the sheet while the felts permit the passage therethrough of the beam. A transmitter is connected to the receiver for transmitting a signal from the receiver in the absence of the sheet. An alarm is connected to the transmitter such that in the event of sheet break, the beam of light is received by the receiver and the signal is transmitted to the alarm so that an alarm signal is generated, indicating that a sheet break has occurred.

Abstract: A method is provided for determining the humidity and temperature of atmospheric air at selected distances along a field of view by passive IR spectrometry. An IR spectrometer is provided. A plurality of IR power densities values received by the spectrometer along the field of view at a plurality of discrete, selected IR wavelengths are measured. A set of equations which equate the measured IR power density to functions of temperature and humidity at the selected wavelengths is provided. From the set of equations the temperature and humidity of the atmospheric air along the field of view at selected range segments along the field of view are calculated.

Abstract: A high temperature optical probe for an optical gas temperature sensor includes a support, a generally conical hollow tip, and a joint physically interconnecting the support and the tip. The tip includes as an electromagnetic radiation emitter a sapphire-free ceramic selected from the group consisting of silicon carbide and silicon nitride.

Abstract: A method and apparatus for non-contact determination of the moisture content in moving or stationary mass of fibrous products such as wood is provided. The method comprises irradiation of a substance with infra-red radiation which is intense enough to introduce microstructural modifications of the substance surface. The moisture content of the substance is determined by analyzing density of these surface modifications. It has been found, that an optical beam may be used in order to quantify the density of the surface modifications. The surface is scanned with the optical beam two (2) times. The first scanning is done prior to the infra-red irradiation; the second scanning is done following the infra-red irradiation. The invented method allows for non-contact, rapid and continuous in-line measurements of the moisture content.

Abstract: The base pairs of a DNA structure are sequenced with the use of a scanning tunneling microscope (STM). The DNA structure is scanned by the STM probe tip, and, as it is being scanned, the DNA structure is separately subjected to a sequence of infrared radiation from four different sources, each source being selected to preferentially excite one of the four different bases in the DNA structure. Each particular base being scanned is subjected to such sequence of infrared radiation from the four different sources as that particular base is being scanned. The DNA structure as a whole is separately imaged for each subjection thereof to radiation from one only of each source.

Abstract: A method for obtaining quantitative compositional information from a multilayer web containing a highly light-scattering component. The compositional information is obtained by measuring and analyzing the transmitted or diffusely reflected infrared spectrum. The method allows for separately determining the moisture content of hydrophobic (non-hydrogen bonding) layers and hydrophilic (hydrogen bonding) layers of multilayer webs. The separate measurements of moisture content can be made simultaneously in moving webs having both types of layers present. The method is used to determine further compositional information such as the thickness of the individual support and gelatin containing layers, plasticizer content, retained solvents content, and the presence of other components in webs, especially photographic webs.

Abstract: A process is provided for obtaining spectral information and quantifying the physical properties of a sample. The process comprises launching polychromatic light having a wavelength ranging from about 100 nanometers to about 2500 nanometers alternately through at least one sample channel and at least one reference channel, through at least one high-efficiency fiber optic switch. The sample and the polychromatic light along the sample channel are directed to a sample cell wherein the polychromatic light is passed through the sample, producing sample spectral information. The polychromatic light directed along the reference channel produces reference spectral information.

Abstract: The condition of the roadway with respect to dryness, wetness, or icing is determined, contact-free by way of reflection measurements of light in the infrared range. The reflected light is measured selectively and simultaneously by a receiver in at least two wavelength regions with the wavelength ranges to be determined being in spectral dependence from the surface condition. Formation of a quotient of the detected signals makes possible an unequivocal statement regarding the respective condition of the roadway surface.

Abstract: The invention relates to a process for the analysis of plastic mixtures by infrared transmission spectroscopy in which the spectra are run while the samples are rotated. This measure improves the accuracy and reproducibility of the spectra and, hence, the determination of individual components of the plastic mixture.

Abstract: A method for visualizing off-surface flows consists of releasing a gas with infrared absorbing and emitting characteristics into a fluid flow and imaging the flow with an infrared imaging system. This method allows for visualization of off-surface fluid flow in-flight.

Abstract: A method and apparatus for enabling analysis of a flowable material enclosed in a transport system having an infrared transparent wall portion. A temperature differential is transiently generated between a thin surface layer portion of the material and a lower or deeper portion of the material sufficient to alter the thermal infrared emission spectrum of the material from the black-body thermal infrared emission spectrum of the material, and the altered thermal infrared emission spectrum is detected through the infrared transparent portion of the transport system while the altered thermal infrared emission spectrum is sufficiently free of self-absorption by the material of emitted infrared radiation. The detection is effected prior to the temperature differential propagating into the lower or deeper portion of the material to an extent such that the altered thermal infrared emission spectrum is no longer sufficiently free of self-absorption by the material of emitted infrared radiation.

Abstract: A fire-perimeter, temperature-differentiating mapping system for creating a temperature-level-differentiated, visually readable outline of a ground fire, which outline is suitable for in-scale registered overlay of a related topographic map for the purpose of aiding firefighters in determining where best to allocate fire-fighting resources.

Abstract: A method for sorting a plurality of diverse objects into groups, each such object being made predominately from at least polyethylene terephthalate and polystyrene and at least two of polyvinyl chloride, polyethylene and polypropylene, the groups consisting at least of objects of like type of polymer identified to be polyethylene terephthalate and polystyrene and at least two of polyvinyl chloride, polyethylene and polypropylene. The method includes three steps. The first step is to irradiate the objects to be sorted with near-infrared radiation. The second step is to measure the diffuse reflectance of the irradiated objects in the near-infrared region to identify the objects as to the type of polymer used to make them. The third step is to direct the objects to their respective groups according to the measurement and identification of the second step.

Abstract: In a method for measuring protein content of whole grain kernels with a near infrared spectrophotometer, reflectance measurements are made at wavelengths shorter than 1600 nanometers. The wavelengths are selected to correspond with absorbance bands of the constituents of the sample. The measurements are encoded into absorbance data and are normalized by subtracting the absorbance value at a first wavelength and then dividing the resulting data by the value at a second wavelength. In accordance with one embodiment, the normalized data is substituted in a formula having coefficients determined by regression from samples having known percentages of protein in the sample to yield the percentage of protein in the unknown sample. In accordance with a second embodiment, the second differential of the absorbance data is determined and the resulting differential values are inserted in the formula having coefficients obtained from the known samples to yield the percentage or protein in the unknown sample.

Abstract: A method and apparatus for inspecting a channel through a workpiece or cooling holes through the surface of a gas turbine engine are disclosed. The gas turbine engine blade is mounted in a fixture such that a heated gas may be forced into the hollow interior of the blade during a heat-up cycle, and after a predetermined period of time, a solenoid valve switches to shut off the heated gas and to permit a chilled gas to be forced into the hollow interior of the blade for a cool-down cycle. An imaging infrared radiometer generates a series of images of the blade during both the heat-up and cool-down cycles. A selected group of parameters are determined from the series of images generated by the IR radiometer and defects within the cooling holes may then be detected by analyzing the parameters, such as a transient response of the infrared signature of the cooling holes during both the heat-up and the cool-down cycles.

Abstract: A passive infrared radiation (PIR) detection system permits data developed by the PIR detection system to be interpreted, to in essence "look into" a protected area and to positively determine the character of any images detected in the protected area. The system includes an array of PIR detectors for monitoring defined zones of the region to be protected. The array of PIR detectors is contained within an enclosure which is further provided with a lensing system which permits the several PIR detectors to monitor respectively assigned zones of the protected region from a single vantage point. The array of PIR detectors operates to develop a series of electrical signals which are then passed on for further processing and interpretation in accordance with various prescribed tests (criteria) which operate to distinguish between an intruder and other legitimate images capable of exciting the PIR detection system.

Abstract: A method is disclosed for evaluation of the transition region of a silicon epitaxial wafer comprising obtaining the waveform of an interferogram signal for reflected light by irradiation the silicon epitaxial wafer with infrared radiation followed by measurement of the intensity of the light of the interference fringe employing a Michelson interferometer and obtaining the extent of the transition region of the silicon epitaxial wafer by measuring the distance between the maximum peak of the waveform in the side burst region in the interferogram signal and the peak adjacent to said maximum peak of the waveform in the side burst region in the interferogram signal and the distance between the maximum peak and the bottom first coming after said maximum peak of the waveform in the side burst region in the interferogram signal, or the difference in height between the maximum peak and the bottom first coming after said maximum peak of the waveform in the side burst region in the interferogram signal.

Abstract: A method and an apparatus for simultaneously measuring each constituent film in a multi-layer coating. Near Infrared Reflectance (NIR) measurements are taken at the peak and reference wavelength for a series of calibration samples. Based on these measurements, a relationship is established between the film NIR and thickness. A measuring NIR spectrometer is supplied with the relationship and a target sample is irradiated with near infrared radiation at each peak and reference wavelength. The measuring spectrometer measures the amount of NIR and computes the individual film thicknesses using the relationship supplied to it. Individual film thicknesses can be visually displayed, and/or directed to the film applying apparatus. If the thickness of an individual film layer deviates from a predetermined valve, the film applying apparatus is manipulated to apply the desired thickness of film.

Abstract: A method of nondestructively identifying regions "R" of high density in a substrate (10) of a bonded matrix of carbon fibers by resistively heating the substrate and taking an infrared image of the heated substrate. Terminals 12, 14, 16 and 18 are connected to a power supply 26 by wires 22 and cable 24 of which they are a part, to effect the heating.

Abstract: A method of detecting pre-spotting is described, comprising meauring the amount of IR light transmitted through a slide test element, using an IR-emitting diode and a photosensitive transistor or photodiode. The amount of transmission is compared against a standard level up until the time when sample dispensing is to commence.

Abstract: A system for detecting fires uses at least two carbon dioxide sensors positioned at spaced locations in a room. Each sensor produces an electrical output signal representative of the carbon dioxide concentration in its vicinity. A computer calculates the ratio of the concentration sensed by each sensor to the concentration sensed by each of the other sensors, and any imbalance in the distribution of carbon dioxide will be reflected in these ratios. Random variations prevent the ratios from being equal, and the magnitude of the random variations is quantized by calculating the standard deviation of the ratios. The ratios are then normalized and compared to a threshold level that corresponds to a chosen false alarm rate.

Abstract: In a passive infrared intrusion detection system, a signal responsive to infrared radiation received from optically divided zones of an area to be monitored is integrated to produce an integral sum. The integral sum is used to generate an alarm indication. The alarm indication is thereby responsive to the energy of the signal responsive to the infrared radiation received, thus improving sensitivity of the detection system without increasing susceptibility of generating a false alarm.

Abstract: A method and apparatus for the detection of pits and abnormalities in various stone fruits. The apparatus transmits a first plurality of beams of light (18) across inspection zone (14) and transmits a second plurality of beams of light (22) across inspection zone (14) in a direction opposite to beams of light (18). As a stone fruit (10) passes through inspection zone (14), a first plurality of sensors (32) and a second plurality of sensors (34) detect the variations in the intensity of the transmitted beams of light. The light transmittance and reflectance characteristics of the stone fruit are analyzed to detect the presence of a pit or internal or external abnormality.

Abstract: A method and apparatus for enabling analysis of a solid material (16, 42) by applying energy from an energy source (20, 70) top a surface region of the solid material sufficient to cause transient heating in a thin surface layer portion of the solid material (16, 42) so as to enable transient thermal emission of infrared radiation from the thin surface layer portion, and by detecting with a spectrometer/detector (28, 58) substantially only the transient thermal emission of infrared radiation from the thin surface layer portion of the solid material. The detected transient thermal emission of infrared radiation is sufficiently free of self-absorption by the solid material of emitted infrared radiation, so as to be indicative of characteristics relating to molecular composition of the solid material.

Abstract: Web flutter in a papermaking machine is monitored by a device which illuminates a portion of the web with infrared light and uses an infrared sensor to monitor the resulting infrared light scattered back from the web. Preferably two infrared light transmitters are used which are angled from each other to insure that light is scattered to the sensor independently of the orientation of the web.

Abstract: A method and apparatus for enabling analysis of a material (16, 42) by applying a cooling medium (20, 54) to cool a thin surface layer portion of the material and to transiently generate a temperature differential between the thin surface layer portion and the lower portion of the material sufficient to alter the thermal infrared emission spectrum of the material from the black-body thermal infrared emission spectrum of the material. The altered thermal infrared emission spectrum of the material is detected by a spectrometer/detector (28, 50) while the altered thermal infrared emission spectrum is sufficiently free of self-absorption by the material of the emitted infrared radiation.

Abstract: A flame detector has a sensor for producing a digital waveform representing a flickering flame. Its turning points are detected and the magnitudes between successive such points are measured. The value of each such magnitude is plotted on a graph whose horizontal axis represents the current value and whose vertical axis represents the immediately preceding value. Points are produced lying in regions away from the diagonal and from the axes. If the detected waveform originates from a regularly varying interfering source, the corresponding points will lie on or near the diagonal. If the interfering source is a waveform undergoing step changes, the corresponding points will lie adjacent to the axes. In this way, discrimination between flames and interfering sources of radiation can be made.

Abstract: For the detection of heat sources within an area to be maintained under surveillance, several scanning units at different scanning stations are linked to a common radiation sensor by respective optical fibre transmission elements. A gating means, such as a rotary mask with an opening, is indexed stepwise to gate each transmission element in turn to the common sensor.

Abstract: A method is provided for precisely and concurrently measuring dynamic engine oil consumption and fuel consumption within an internal combustion engine in an automotive environment on a real time basis. Nonradioactive tracer compounds, such as bromine or chlorine in the form of organic bromo- or chloro-compounds are added to the engine oil in small amounts. Upon complete combustion, the bromine or chlorine is converted into either hydrogen bromide or hydrogen chloride. A sample of the exhaust gases generated by the internal combustion engine and comprising the hydrogen bromide or hydrogen chloride is collected and maintained at a pressure where distinction between an absorption line of the tracer specie and the absorption lines of a related isotopic species is discernible. Monochromatic radiation is then transmitted through the gaseous sample at the frequency of an absorption line particular to the tracer specie.

Abstract: A system for public display of ultraviolet radiation levels wherein said radiation is collected and measured by one or several optical collectors or sensor assemblies at remote sensing stations. Optical fibers receive and then convey the radiation of the sun through a filter and onto a photovoltaic sensor, measuring the intensity of the ultraviolet radiation. An electrical signal proportional to the ultraviolet radiation is produced with the signal being amplified and either used directly as analog data or converted to a digital signal for the modulation of a radio transceiver. The signal is transmitted to a transceiver of a central data processing station, where it is processed. The processed signal is retransmitted to a receiver in which the processed signal carrier is demodulated and the signal fed to a display station providing the level of exposure to the public.

Abstract: A large area pyroelectric joulemeter for measuring the pulsed beam output of a laser. The joulemeter employs a pyroelectric detector element with front and rear conductive surfaces forming electrodes, a relatively massive mounting block with relatively high thermal conductivity and an epoxy adhesive for securing the detector element to the mounting block, the epoxy having relatively high thermal conductivity so that heat can be quickly dissipated out of the detector element. An internal recess in the mounting block accommodates a trimming capacitor and resistor for adjusting the voltage sensitivity of the detector assembly to a constant value. The detector assembly is removably installed within an outer housing having a main base portion and a removable bezel.

Abstract: The intrusion detection system of the invention, in which three pyroelectric detectors are disposed in line with a interval and an adjoining two of the three pyroelectric detectors are electrically connected to cancel electrical charges generated by each pyroelectric detector, detects intrusion of an infrared ray radiating object such as a human body for example by output signals outputted from the adjoining two and the other of the three pyroelectric detectors or by output signals outputted from the pyroelectric detector disposed at the center and adjoining one and output signals outputted from the one disposed at the center and adjoining another one of these pyroelectric detectors, so that precise and secure intrusion detection is possible by reducing erroneous signals generated by those pyroelectric detectors due to variation of the atmospheric temperature and the like.

Abstract: A photoelectric intrusion detector for detecting the interruption by an intruder of a monitoring beam of optical radiation such as an infrared radiation includes circuitry for preventing the generation of a false alarm when the optical beam is attenuated during its propagation through space due to fog or the like. This false alarm preventing circuitry is designed so that when the attenuation of a beam of optical radiation during its propagation through space is increased due to the occurrence of fog in cloudy weather, the occurrence of a false alarm due to the attenuation of the pulsed light in cloudy weather is prevented by decreasing a comparator reference value to follow the decrease in the level of a light receiving signal, correcting the gain of AGC amplification to maintain constant the level of a received light signal or correcting the level of a received light signal which follows a received light initial value.

Abstract: A digital control circuit uses a single infrared detector to control the clock pulse on a digital counter so that the sensitivity control is based on the length of time a change in infrared radiation persists. A pyroelective detector is located in a voltage divider and the intermediate voltage of the divider is digitally compared to the intermediate voltage in a fixed divider as a digitaly controlled pulse is applied to both dividers. Either an increase or a decrease of infrared radiation causes the digital circuit to permit the counter to be activated.

Abstract: A device, for simulating temperature effects at the interface of a head-to-medium interface, is comprised of a unitary block of material which transmits radiation in the infrared (IR) region of the electromagnetic spectrum and which has a wear-resistant property substantially approximating that of the material of an actual magnetic head to be simulated. The unitary block is shaped to have (1) a first forwardly facing surface substantially approximating the dimensions and contour of the working surface of the head to be simulated, and (2) a second rearwardly facing surface substantially approximating the dimensions and contour of a light-transmitting surface of a positive spherical lens the focal plane of which coincides with the forwardly facing surface. Sapphire is selected as a material having a suitable IR-transmitting property and a wear-resistant-property commensurate with one wear-resistant properties of alloy and ferrite materials commonly used in the manufacture of a video magnetic head.

Abstract: A flame detecting device indicates the presence or absence of a flame. The detecting device includes both an IR detector for sensing the IR frequencies of the flame and a UV detector for sensing the UV intensity of the flame. Information is stored defining IR frequency and UV intensity standards. A microcomputer is operatively connected to the IR and UV detectors and compares the two detector outputs to the two respective standards in accordance with a program establishing defined conditions in terms of IR frequency and/or UV intensity that must be met for a flame present or flame absent signal to be rendered on a bar graph display.

Abstract: An optical filter and detector, and a related method for its operation, in which signal photons are admitted into a detector cell and selectively excite atoms or molecules of a vapor to a selected metastable state. An illuminating laser then photoionizes a large proportion of the excited atoms or molecules, and the resulting free electrons are collected as a measure of the number of incident signal photons. The initial excitation step to a metastable state is highly sensitive to the wavelength of the signal photons and therefore acts as a narrowband filter.

Abstract: A passive analog equalizer is connected to the output of an infrared detector to provide increasing pyroelectric detector sensitivity with increasing target frequency in order to provide a detection sensitivity which is substantially flat over the target velocity range of interest. An interruptable modulator is connected to the equalized pyroelectric detector signal to shift its frequency upwardly in order to provide negligible drift, fast recovery from transients, and the ability to quickly shut down the modulator when a transient occurs. A transient detector is operative in response to transients in the pyroelectric detector output signal to provide a window during which the modulator is interrupted in order to prevent transient induced false alarms.

Abstract: A method of detecting fires utilizing its flicker frequency spectrum provides a standard theoretical flicker frequency spectrum which is compared to the real time spectrum over a 2 second time period. The comparison includes whether or not the real time fire spectrum deviates from the idealized fire spectrum by a minimum amount and has further discrimination against false fire signals, including the extent of time of the real time spectrum is outside a predetermined window and a limit on maximum deviations.

Abstract: A method and apparatus for element specific detection in chromatogragphic eluents. The apparatus is comprised of a radio frequency discharge between electrodes in helium, and utilizes a low-resolution plasma emission spectrometer to monitor selected spectral emissions produced when the helium discharge decomposes and excites the atomic constituents in chromatographic column effluents. The spectrometer is tuned to an atomic emission line in the near-infrared portion of the spectrum, and the emission intensity from the discharge region of a selected line is used to monitor the concentration of the element producing that line. Acceptable detector sensitivity is achieved by the use of a high-throughput optical system. Selectivity is achieved by a combination of correct line selection, plasma and carrier gas purification, and plasma gas doping.

Abstract: The presence of an operating helicopter within a given field of view is remotely and passively monitored by optically imaging the field of view at a focal surface, using an infrared detector to produce an electrical signal. The electrical signal is filtered with a narrow pass-band having a center frequency which is adjustable over a range which spans the respective modulation frequencies of characteristic infrared radiation emitted by the rotating blades of each of a plurality of helicopters of different type. Provision is made to indicate such component of the electrical signal as survives the filtering step.

Abstract: The present invention relates to improvements in test methods for determining if eggs, seeds or the like are fertile. This is accomplished through the use of thermography equipment which senses a temperature rise characteristic of a fertile egg or seed. The sensing can be visually observed or a thermograph can be made of the observation.

Abstract: An interferometric sensor (10) employs a sensing optical fiber (12) and a reference optical fiber (14). The sensing fiber (12) has a coating 16 thereon responsive to radiated thermal energy while the reference fiber is shielded therefrom. Both the sensing and reference fibers are subjected to the same ambient environment so that both fibers are subjected to heating by convection or conduction in essentially the same amounts. As a result, the sensor (10) is substantially nonresponsive to convected or conducted thermal energy while being highly responsive to radiated energy, particularly in the 6-30 micron wavelength region.

Abstract: A horizon sensor having a pair of adjacent infrared detectors which view the earth's horizon either statically or by scanning is provided with a second order radiance correction to reduce errors in determining the true position of the horizon due to radiance variations of the earth due to changes in latitude and seasons particularly at lower altitudes. The second order correction is empirically determined from a large number of horizon profiles, and in two illustrative examples for different types of sensors, the correction may be readily obtained from a linear function related to the peak radiance of the horizon profiles.

Abstract: Disclosed is a method for rapid and accurate qualitative and quantitative analysis of finishing agent applied onto the surface of a glass fiber substrate. This method comprises placing a glass fiber substrate to be tested in a Fourier transform infrared spectrophotometer equipped with a diffuse reflectance measuring device, irradiating said glass fiber substrate with infrared ray and carrying out qualitative analysis of finishing agent on the surface of the glass fiber substrate from wave number of infrared absorption peak produced at the irradiation and quantitative analysis of the finishing agent from intensity of the infrared absorption peak.