Abstract: A method and apparatus for detecting and quantitatively measuring a molecular species of gaseous material in a sample to be analyzed are provided. Light containing incoherent infrared radiation is collected, collimated and transmitted by a light conditioning means to a primary filtering means. The primary filtering means selectively transmits light having a frequency range in the region of an absorption band for a molecular species to be detected. A secondary filtering means, adapted to receive the filtered light, transmits light at a plurality of discrete frequencies, providing a detectable signal, through the gaseous material. The intensity of the signal changes in proportion to the concentration of the molecular species. Means are provided for measuring and recording the magnitude of the signal intensity change.

Abstract: A method and apparatus for determining the temperature of gaseous materials are provided. Light produced by scattering in a gaseous material and having spectral components periodic in frequency is collected, collimated and transmitted by a light conditioning means to an interferometric means. The interferometric means selectively separates periodic spectra from the light and transmits the spectra in the form of a detectable signal containing first and second branches of the spectra. Means are provided for measuring the intensities of the branches and detecting and recovering the intensity ratio thereof, which is correlated with the temperature of the gaseous material.

Abstract: A method and apparatus for spectroscopic gas analysis are provided. Plural beams of monochromatic radiation are directed through gaseous material. A tuning mechanism adjusts the frequency difference between the radiation beams to equal substantially an odd integral submultiple of the frequency difference between adjacent spectral components of the periodic spectrum for a preselected constituent of the gaseous material. Radiation scattered by the gaseous material is received by a filtering mechanism adapted to transmit selectively a detectable signal composed of a single superimposed spectral component of the spectrum. The signal is received by a detecting means which indicates the intensity thereof.

Abstract: Light having spectral components periodic in frequency is collected, collimated and transmitted by a light conditioning means. Secondary interferometric means, adapted to receive the light, selectively separate preselected spectra therefrom and send the light devoid of the separated spectra to a primary interferometric means. The primary interferometric means selectively separates periodic spectra from the light and transmits such spectra in the form of a fringe which provides a detectable signal. A multipass means directs the signal back through the primary interferometric means, whereby the contrast ratio of the signal is increased. A modulating means modulates the phase difference between interfering rays of light transmitted by the primary interferometric means so as to vary the intensity of the fringe. The intensity variation of the fringe is detected by a phase sensitive detection means, and the resultant signal is displayed by an indicating and recording means.

Abstract: Light having spectral components periodic in frequency is collected, collimated and transmitted by a light conditioning means. Secondary interferometric means, adapted to receive the light, selectively separate preselected spectra therefrom and send the light devoid of the separated spectra to a primary interferometric means. The primary interferometric means selectively separates periodic spectra from the light and transmits such spectra in the form of a fringe which provides a detectable signal. A multipass means directs the signal back through the primary interferometric means, whereby the contrast ratio of the signal is increased. A modulating means modulates the phase difference between interfering rays of light transmitted by the primary interferometric means so as to vary the intensity of the fringe. The intensity variation of the fringe is detected by a phase sensitive detection means, and the resultant signal is displayed by an indicating and recording means.

Abstract: A method and apparatus for analyzing light are provided. Light having spectral components periodic in frequency is collected, collimated and transmitted by light conditioning means to a first interferometric means. The first interferometric means selectively separates a preselected periodic spectrum from the light and transmits such spectrum in the form of a fringe having an intensity derived from and substantially equal to the combined intensities of the transmitted spectra. A second interferometric means adapted to receive the fringe transmits the preselected periodic spectrum thereof in the form of a modified fringe providing a detectable signal. The portion of total intensity of the modified fringe derived from the combined intensities of the transmitted spectrum is greater than that of the fringe in the presence of unwanted spectra.

Abstract: A method and apparatus for spectroscopic gas analysis are provided. Two coherent beams of monochromatic radiation are directed through gaseous material. A tuning mechanism adjusts the frequency difference between the radiation beams to equal substantially the rotational frequency of a preselected constituent of the gaseous material. Radiation scattered by the gaseous material is received by a filtering mechanism adapted to transmit selectively an anti-Stokes signal generated coherently during scattering. The signal is received by a detecting mechanism which indicates the intensity thereof.

Abstract: A method and apparatus for detecting and quantitatively measuring a molecular species of gaseous material in a sample to be analyzed are provided. Light containing incoherent infrared radiation is collected, collimated and transmitted by a light conditioning means to a primary filtering means. The primary filtering means selectively transmits light having a frequency range in the region of an absorption band for a molecular species to be detected. A secondary filtering means, adapted to receive the filtered light, transmits light at a plurality of discrete frequencies, providing a detectable signal, through the gaseous material. The intensity of the signal changes in proportion to the concentration of the molecular species. Means are provided for measuring and recording the magnitude of the signal intensity change.