Abstract: A photomultiplier (10) with an elongated rectangular, cathode (20) tilted with respect to the inlet opening (14) is alternately illuminated by a measuring light beam (36) and a reference light beam (40). The measuring light beam (36) and the reference light beam (40) extend in a plane parallel to the longitudinal sides of the cathode (20) and impinge upon the cothode (20), such that they illuminate the same areas of the cathode (20).

Abstract: A spectrophotometer comprising a light source, a spectroscope which separates the light of light source depending on the wavelengths, chops the light into the first and second light beams and allows the light beams to pass through the reference cell and sample cell, a photodiode which alternately receives the light beams from the reference cell and sample cell, a variable gain amplifier which amplifies a light current of photodiode, an A/D converter which converts and guides the reference output and sample output as the digital values synchronously with the chopping period, and a again setter which sets the gain of the variable gain amplifier depending on the reference output value from the A/D converter.

Abstract: The apparatus and method of the invention are applied to the generation of alternating sample, dark, reference and dark beams for direction of said sample and reference beams into an integrating sphere which comprises detecting means and a reference source, for spectroscopic analysis of a sample contained in a sample cell which is operatively associated with said integrating sphere; to the generation of digital control signals attendant the generation of said beams; and to the processing of the multiplexed, sample analysis results analog data signal, as provided by the detecting means, by aligning a digital control signal therewith in time and further operating upon the thusly aligned data signal to precisely calculate the sample analysis results therefrom.

Abstract: In a double-beam photometer comprising a light source providing a light beam, detector means, a sample area, optical means for guiding the light beam as a measuring light beam through the sample area onto the detector means, means for guiding the same light beam as a reference light beam onto the detector means while avoiding the sample area, and chopper means disposed in a splitting location for splitting the light beam into the measuring light beam, which are combined into one path of rays in a recombination location, after the measuring light beam has passed through the sample area, with the splitting location and the recombination location being spatially close to each other. The chopper means has a single chopper which simultaneously effects the splitting and the combination of the measuring and reference light beams.

Abstract: A spectrophotometer having functions of both of a double-monochromator and a single-monochromator including a light source, a first spectroscope having a first slit through which light from the light source passes and a first dispersion element for dispersing the light from the first slit, a second spectroscope having a second slit for receiving light dispersed from the first dispersion element for dispersing the light from the second slit, and a third slit for receiving the light dispersed from the second dispersion element. A sample compartment is provided for transmitting the light from the first dispersion element or from the third slit directly to a detector or through a sample to the detector. An optical unit is provided for changing transmitting light paths between a first light path for transmitting the light from the first dispersion element to the sample compartment through a fourth slit and a second light path for transmitting the light from the third slit to the sample compartment.

Abstract: Self-normalization of laser spectrometers is provided by I"/I laser modulation and detection. A single tunable diode laser is frequency modulated by a high S/N ratio triangle wave, mechanically chopped, passed through an isothermal in-line gas and reference chamber absorption cell, and synchronously detected to provide the I" and I signals. The preferred embodiment discloses isotopic ratio measurements. The invention has application to quantitative trace gas measurements generally.

Abstract: A method for the phase synchronization of step-drive-controlled equipment, in particular of optical modulation devices for multiple-beam spectrophotometers.Starting with the phase comparison of a synchronization signal formed from a sensor signal produced by a fixed phase difference from information signals of the device, the phase relationship of the commutator signals of the stepping motor is controlled with a predetermined reference signal.

Abstract: A photometer in which a measuring phase, a reference phase and a dark phase are produced by means of a chopper. These phases are staggered in time, so that a single detector can be provided for all phases. In the photometer the object to be measured is situated between two light conductors, the one light conductor leading to the detector and the other light conductor leading to the chopper input. The chopper output is carried by an additional light conductor to the detector.

Abstract: A method for the phase synchronization of equipment controlled by stepping drives, especially optical modulating systems for multiple-beam spectral photometers. Each time that the equipment is started up, a reference signal is made synchronous with a synchronizing signal which is derived from a sensor signal of the apparatus which is locked in phase with the intelligence signal. For a purely electrical correction the phasing between the intelligence signals and the synchronizing signal is set once. In the event of a phasing error between the synchronizing signal and the reference signal the reference signal is reset.

Abstract: Method and apparatus for measuring light by frequency-modulating a light signal from a sample being measured and demodulating the modulated signal in synchronism with the modulating operation, wherein there is provided a delay circuit which produces a series of pulses for synchronous rectification of the modulated signal in response to and with a predetermined time delay after the modulating operation, so that before measurement of a specific sample the delay time is changed so as to determine the phase of the synchronous rectification pulses most suitable for measurement of the specific sample.

Abstract: A dual wavelength spectrophotometer produces a relatively small, high power, high duty cycle light spot from a single relatively low power multi-chromatic light source. A Xenon arc lamp light source is focused by an ellipsoidal mirror onto a rotating partially reflective optical chopper. The chopper comprises a wheel having mirrored segments alternately separated by transparent segments. Light reflected by the mirrored segments passes through a first monochromator which produces a first monochromatic light beam. Light transmitted through the transparent segments passes through a second monochromator and emerges as a second monochromatic light beam having a wavelength different from the wavelength of said first monochromatic light beam. The first and second monochromatic light beams are recombined into a single dual wavelength light beam that is reflected through a sample to be analyzed. Reflective front surfaces are employed throughout the system in order to minimize power loss.

Abstract: A spectrophotometer provided with a plurality of integrating spheres of different types which can be selectively and exchangeably used in accordance with the type of a sample to be measured and the purpose of the measurement.

Abstract: The optical measurement signals in a flame atomic absorption spectrophotometer are first amplified in a substantially linear variable gain amplifier. The gain of the variable gain amplifier is adjusted to provide a predetermined magnitude of output signal during a calibration phase of the spectrophotometer. The resultant output signals from the variable gain amplifier are then converted to a logarithmic function in a logarithmic amplifier during optical absorption measurements.

Abstract: In a spectrophotometer having an optical beam chopped into dark and light segments, a computer controlled system is described for determining background signal due to stray light, photomultiplier dark current, offsets of photometric amplifiers and other components, and the like and for subtracting this background signal from the overall signal so as to leave only the desired light measurement. The same computer system also sets the signal level automatically for highest resolution. Furthermore, the same computer acts as an analog to digital converter by successive approximation to supply the photometric signal to the microprocessor unit. Since the same components are involved in all these functions both analog and digital offsets of the components are automatically cancelled.

Abstract: In a ratio-type double-beam infrared spectrophotometer, an output signal of the photodetector is frequency discriminated to derive therefrom a component having a fundamental frequency f corresponding to at least one of the sample and reference beam intensities and another component having a frequency 2f corresponding to at least the other beam intensity, and these frequency components are computed to determine the ratio of the sample beam intensity to the reference beam intensity. According to the invention, the component of fundamental frequency f is synchronously rectified into a rectified signal which is further differentiated into a differential value, the differential value is subtracted from the rectified signal to give a signal which is compensated for rapid changes of spectral absorption due to the presence of H.sub.2 O and CO.sub.2 in the beam paths during wavelength scanning and is used as the f-component signal.

Abstract: A double-beam spectrophotometer for spectral analysis of a sample in the infrared region is provided in which to eliminate errors in measurement of the absorbance of the sample caused by undesired thermal radiation from the sample itself, first and second sectors are used for division and recombination of beam paths and coordinated such that a detector which receives a beam along the combined beam path produces output signals consisting of components having a frequency f associated with the cycle of operation of the sectors and components having a frequency 2f, those components having frequencies f and 2f are independently derived out of the detector output signals, and the ratio of the components is computed, thereby obtaining the ratio of intensity of sample beam to reference beam independent of the undesired thermal radiation.

Abstract: In a spectrophotometer of double beam type using automatic gain control, preparatory scanning is first carried out by scanning reference and sample cells with radiation of varying wavelengths both in an empty state, and controlling the gain of a photo detector at each wavelength such that a detector output responding to a sample cell transmitted beam may become constant while storing a detector output responding to a reference cell transmitted beam. Measurement of a sample material is then carried out at each wavelength by scanning the reference cell and the sample material-charged sample cell, reading out the reference output stored in the preparatory scanning stage as a reference voltage, and controlling the gain of the detector such that a detector output responding to a reference cell transmitted beam may be equal to the reference voltage.

Abstract: A double-beam spectrophotometer which uses an integrating sphere for measurement of the total reflected light from a sample or only the diffuse reflection component thereof. The sphere is provided with a first pair of windows in which a sample and a reference are detachably and exchangeably set and a second pair of windows through one of which one of a sample and a reference light beam enters the integrating sphere so as to impinge perpendicularly on said sample or reference set in one of said first pair of windows, while through the other of said second pair of windows the other of said sample and reference light beams enters said integrating sphere to impinge aslant on said reference or sample set in the other of said first pair of windows. The positions of said sample and reference are exchanged in accordance with the type of measurement to be made.

Abstract: In atomic spectrophotometers comprising a source of radiation characteristic of an element to be detected in a sample, a monochromator for selecting a desired spectral line from radiation received from the source by the sample, and a detector for producing an output signal from the monochromator output radiation, the monochromator is accurately tuned to the desired line to obtain a maximum detector signal, and simultaneously, the gain of the detector is adjusted to keep the signal magnitude within the best working range of subsequent signal processing circuits. In accordance with the present invention, both adjustments are made simultaneously by comparing an amplified detector signal with a desired reference signal level corresponding to the best signal magnitude, and using the difference between them to adjust the gain of the amplified detector signal in a closed loop control system to continuously equalize the amplified detector signal with the reference level.

Abstract: In atomic absorption spectrophotometer, a reference path may be provided for radiation which excludes the flame. This radiation provides a signal from a detector which varies only with the instrumental drift produced by variations in the radiation source brightness and by variations in detector gain. The signal can be used to compensate for drift in other signals received through a sample path including the flame. In the present invention, radiation passes through the sample path continuously during measurement, and only through the reference path between sample measurements. Movable mirrors shift the radiation between the paths upon externally applied commands. Conveniently, the reference path measurement is made while the flame is stabilized during the change between samples. The reference path measurements are stored and used to correct for drift.

Abstract: In a spectrophotometer of double beam type comprising a radiation source, reference and sample cells, a photo detector, and beam path switching means, a current-voltage converting amplifier and a logarithmic amplifier in parallel connection are connected to the photo detector. In measuring the transmittance of a sample material in the sample cell, an output of the detector responding to a sample cell transmitted beam is directly supplied to the logarithmic amplifier without undergoing current-voltage conversion while an output of the detector responding to a reference cell transmitted beam is supplied to the current-voltage converting amplifier without undergoing logarithmic amplification.

Abstract: A double-beam spectrophotometer comprising a light source, a monochromator, optical means for causing the monochromatic light beam from the monochromator to alternately advance along a pair of optical paths, the axes of which intersect generally perpendicularly to each other, a pair of cells each disposed in one of the two optical paths, and a photoelectric detector disposed at or adjacent the point of intersection of the pair of optical paths.

Abstract: A spectrophotometer which can be used selectively as a single-beam and a double-beam type and comprises a light source, a monochromator, a chopper mirror for causing the monochromatic light beam from the monochromator to alternately advance along a first and a second path, in which a reference and a sample cell are disposed respectively, a beam combiner for causing the alternate beams to advance along a common path leading to a photoelectric detector, and a mirror movable for selective positioning in and out of the monochromatic light beam between the monochromator and the chopper mirror.

Abstract: The accuracy of the ratio between two time-varying quantities represented by electrical signals, such as the sample transmission (or absorption) signal and the reference signal in a double-beam, ratio-recording, infrared spectrophotometer, is impaired if the electrical signals are subject to inconstant phase shifts. The present invention counteracts the effect of phase shift variations, whatever their origin, by alternately reversing the order in which an elemental component of one quantity is made to occur with respect to an elemental component of the other quantity so that the said effect reverses in sign when the order is reversed and substantially cancels out when the respective elemental portions are combined to form the numerator and the denominator of the ratio. The invention is particularly described with reference to a spectrophotometer of the type referred to.

Abstract: A detector for use in optical measuring instruments such as a double-beam spectrophotometer, comprising a photoelectric element having a photosensitive surface and a beam mixer disposed adjacent the photosensitive surface for causing each of two alternate light beams to be projected evenly and uniformly onto the photosensitive surface of the photoelectric element thereby to eliminate errors which would otherwise be caused in the result of measurement due to local difference in sensitivity of the photosensitive surface of the photoelectric element. The beam mixer comprises a symmetrical pair of light diffusing plates so arranged as to form a roof-shaped configuration and a tublar body having one end opening closed by the pair of light diffusing plates and the opposite end opening closed by the photosensitive surface of the photoelectric element.

Abstract: A light chopper for chopping the monochromatic light beam of a spectrophotometer system, has a rotatable shaft driven by a synchronous motor at a frequency proportional to the power line frequency. An aperture bearing disc rotates with the shaft in relation to a photocell/detector array for generating digital timing signals for use by a microcomputer to control the tasks of the spectrophotometer system in synchronism with line frequency. The microcomputer monitors line frequency for responsively programming a programmable divider for generating an index signal for proportionally sequencing the wavelength of the monochromatic beam through a predetermined spectral range.

Abstract: A spectro-photometer having a calibration mechanism and a wavelength-range changeover mechanism is disclosed which is equipped with an operation panel for setting measuring frequencies and function modes, is controlled by a microcomputer to be subjected to the calibration and the changeover of wavelength range in a predetermined order, conducts a predetermined arithmetic operation on the basis of photometric values measured by the spectro-photometer, and further comprises two display elements mounted on the operation panel for performing the following display operation in accordance with a command from the microcomputer. That is, in the calibration period, a code showing that the spectro-photometer is now subjected to calibration, is displayed on one of the display elements, and the number of remaining check items is displayed on the other display element.

Abstract: In a spectrophotometer including a photomultiplier tube and an operational amplifier responsive to the current from the photomultiplier tube for generating a DC voltage proportional to light intensity, a method and means for simultaneously compensating for the dark current of the photomultiplier tube and the offset of the operational amplifier so that the output voltage of the operational amplifier is zero volts under dark conditions.

Abstract: A method and means for operating log converter circuits in which the method comprises the steps of sequentially conducting to the input of the log converter circuit signals representing a known transmittance (T) of 100% T, 10% T, 1% T, and 0.1% T, these signals covering the range of operation of the log converter circuit, storing the outputs of the circuit as signals representing an absorbance (A) of 0A, 1A, 2A, and 3A, respectively, conducting to the input of the log converter circuit an unknown signal, and utilizing a microcomputer to perform a linear interpolation of the output of the circuit with the unknown signal applied thereto using the previously stored 0A, 1A, 2A, and 3A signals.

Abstract: A two beam alternating light colorimeter is disclosed wherein a light beam passing through a lens system having a shutter is periodically deflected by a pivoting mirror. In a first non-deflecting position of the pivotable mirror a first measuring beam is created which passes through a first measuring cell and is guided to a common photo cell. In a second deflecting position of the mirror a second measuring beam is created which is guided through a second measuring cell to the same photo cell. Signals from the photo cell are connected through a controlled switching element to an analog memory. A computing circuit is provided which connects to an output of the analog memory and also to the photo cell. The switching element connects the first measuring signal to the analog memory when the mirror is in a non-deflecting position and opens when the mirror is in a deflecting position. The computing circuit compares the signals corresponding to the first and second measuring beams.

Abstract: Apparatus for determining the concentration of the various components of a sample, which includes a spectrophotometer for receiving a sample to be analyzed and performing extinctions of the sample at a plurality of preselected wavelengths to form a sample spectrum; memory devices for storing a standard spectra of each of the individual components; circuitry for weighting the sample spectrum at different wavelengths in conformity with each of the standard spectra and providing estimated values of the concentrations of the components from the sample spectra thus weighted; circuitry for reconstructing the sample spectrum as a linear combination of the estimated values of the concentrations and the standard spectra; a subtractor for forming a difference spectrum from the sample spectrum and the reconstructed sample spectrum; circuitry for weighting the difference spectrum at different wavelengths in conformity with each of the standard spectra and providing corrective values of the concentrations of the component

Abstract: In a dual beam atomic absorption spectrometer having a dedicated microcomputer, improved calibration constants are obtained from either two or three known concentration values by finding a number of constants equal to the number of samples such that when the excess over one of the absorbance of that sample of known concentration multiplied by a second constant is divided into the first constant times the absorbance raised to a power one less than the number of samples or in the case of three samples the difference between that value and a third constant times the absorbance, for each measured sample, the result is equal to the known concentration of the sample.

Abstract: In the double-beam spectrophotometer, two light beams, a reference beam and a sample beam, are used. Optical signals in the light beams are converted into electrical signals. The magnitudes of a reference signal and a sample signal are compared. A voltage to be applied to a photoelectric converting means is adjusted on the basis of the difference signal between the larger signal of the compared signals and a reference voltage so that the magnitude of the larger signal is substantially constant. The spectrum displayed by a recorder is obtained by the ratio of the reference signal to the sample signal. Since the larger signal is controlled to be substantially constant, when the sample signal is larger than the reference signal as in the case of a difference spectrum, the photoelectric converting means is not saturated and a wide photometering range is secured.

Abstract: A sensitive laser spectroscopy measurement system having a laser radiation source and a dual beam and detection scheme that allows for the measurement of small intensity differences between a probe beam and a reference beam resulting from the absorption, gain or scattering of the probe beam by a medium placed in its optical path. The system attains measurement sensitivities of less than 10.sup.-4 when the laser radiation source for the probe and reference beams is modulatable. Further included within the system is a prism placed in the optical path of the laser beam before the beam splits into the probe and reference beams and a detector for each beam. The detectors are electrically connected to a sensitivity differential amplifier and an oscilloscope for displaying the intensities of the beams.

Abstract: The reflectivity compensating apparatus is utilized in a dual wavelength spectrophotometer wherein a chopper mirror, having alternating mirror segments and open spaces equal in area, cuts through a light beam from a light source and the mirror segments reflect light through a liquid sample in a sample container to a photodetector having an output channel. The reflectivity of each mirror segment varies slightly from the other segments.

Abstract: Monochromatic light emitted from a monochromator is split into two light beams. These light beams are detected by a photodetector and converted into corresponding electric signals after having been transmitted, respectively, through a sample to be analyzed and a reference placed in the respective beam paths. The signal corresponding to the light beam transmitted through the sample and the signal corresponding to the light beam transmitted through the reference are converted into digital signals which are subsequently stored in respective digital storages or memories. The signal corresponding to the light beam transmitted through the reference is compared with a value in a predetermined range. The resultant value is then converted into an analog signal for operating a sensitivity regulator thereby to adjust the sensitivity of the photodetector. Thus, the signal corresponding to the light beam transmitted through the reference (reference light signal) is so controlled as to lie in a predetermined range.

Abstract: Method for optically analyzing a specimen by using two light beams comprises steps of initiating automatically wavelength scanning operation when a predetermined time has elapsed after the switching-on of a power source, sampling a ratio between a reference light intensity and a specimen light intensity during the wavelength scanning operation when no specimen to be measured is placed in the sample cell, and storing signals derived from the sampling operation in a volatile memory. When the specimen is to be measured or analyzed, the measure signal representative of ratio between the reference light intensity and the specimen transmitting light intensity which are produced or the wavelength scanning operation proceeds is corrected by the corresponding signal read out from the volatile memory in accordance with the wavelength of the measure signal, and the corrected signals are processed as the error-free measure signal.

Abstract: A spectrometer for measuring the spectra and concentration of airborne chemicals at long ranges wherein the optical signals may be occluded by dust. A single lasing medium is utilized both for producing a transmitted optical signal and for amplifying a received optical signal, the frequencies of radiation of the transmitted and received optical signals being offset as the radiation propagates to a distant reflector and back to the lasing medium. The frequency offset is obtained by sweeping the transmitted frequency at a rate commensurate with the round trip propagation time whereby the offset is sufficient to place the received frequency at a peak at the amplifying spectrum of the lasing medium. A laser containing the laser medium further incorporates an interferometric structure within the optical path for sequentially shifting the frequency of oscillation to produce a comb spectrum for sampling the spectra of the chemicals to provide identifying signatures thereof.

Abstract: In a scanning spectrophotometer, in which a narrow wavelength band of radiation can be selected from a range of wavelengths for transmission alternately through a sample cell and a reference cell, continuous automatic baseline correction is provided. A pulse train signal is generated, wherein the number of pulses represents the ratio of a parameter (e.g., intensity) of the radiation transmitted, respectively, through the sample and reference cells. A ratio of unity represents the baseline, and deviations from the baseline are indicated by changes in the number of pulses in the pulse train. Digital information indicative of baseline deviations is stored in a memory device when the spectrophotometer is being calibrated, and is retrieved from the memory device during operation of the instrument for sample analysis. The retrieved information generates a correction signal, which provides a continuous baseline correction.

Abstract: An improved optical chopper, developed particularly for use in a double beam atomic absorption spectrophotometer, receives light beams from two separate sources and sequentially switches them into two separate paths and instantly thereafter the second light beam enters the first path, followed immediately by the first beam entering the second output path and then the second beam entering the second path; alternatively, the chopper is arranged so that the first light beam enters the first output path followed by the first light beam entering the second output path, and then the second light beam enters the first path and the second light enters the second path; also, during one segment of the choppers cycle, both beams are blocked from both output paths.

Abstract: A spectrum analyzing system measures or analyzes the colorimetric properties of a test sample at a preselected wavelength or range of wavelengths within the ultraviolet, visible, and near infrared regions. The system includes a spectrophotometer provided with a wideband light source, optical devices providing a sample light path and a reference light path, a chopper wheel allowing light to be directed alternately along the sample and reference paths interspersed with dark periods during which no light travels along either path, a dispersion grating for dispersing the light from both paths, a series of neutral density filters for limiting to various degrees the amount of light traversing each path, and a linear array of photodiodes for detecting the dispersed light at different wavelengths.

Abstract: A pair of optical beams of radiant energy from separate paths in a spectrophotometer are coaxially merged into a single composite beam with an optical member which resembles a coarse echelette grating. A reflective surface which includes the surfaces of sidewalls within a plurality of parallel grooves is disposed on the optical member. The grooves are arranged in a lateral array and are generally V-shaped cross-sectionally. The beams to be combined are directed upon the sidewalls and the composite beam is emitted therefrom in accordance with the law of reflection. When the beams to be combined include non-collimated rays, shadowing is provided by the portion of the optical member between adjoining sidewalls of adjacent grooves to reduce flare. Furthermore, image aberrations as caused by off-axis operation due to use of a spherical mirror in the beam combining arrangement, are substantially corrected by the optical member.

Abstract: A cross-talk balancing circuit for double-beam spectrophotometers is disclosed. The circuit includes means to measure in four successive sample periods the sample plus sample re-radiation (S + s), reference radiation plus reference re-radiation (R + r), sample re-radiation (s) and reference re-radiation (r). The detector, however, does not respond quickly so it introduces cross-talk into each measurement. Electronic phasing circuitry selects the time when the detector output is sampled so that the cross-talk in the measurements is equalized permitting it to be subtracted out of the measurement thereby leaving a remainder which accurately corresponds to the desired quantities S and R.

Abstract: An atomic absorption spectrophotometer incorporating discrimination against "background" absorption, i.e., absorption not caused by the resonant line absorption by the element being measured. The device includes a resonant line emitting source (e.g., a hollow cathode lamp) and a continuous spectrum light source (e.g., a deuterium lamp), a monochromator and a detector system. The improvement comprises a specific chopper arrangement which sequentially causes: (a) the resonant line light from the hollow cathode lamp to go to the sample path, (b) this light to go to the reference path, (c) the continuous spectrum light from the deuterium lamp to go to the reference path, and finally (d) the continuous spectrum light to go to the sample path. By comparing the light intensities during intervals (c) and (d) the effect of the background absorption can be determined and compensated for so as to determine the relationship between (a) and (b) free of the effect of such background absorption.