Simultaneous interferometric transmission of periodic spectral components

Claim 2

Apparatus for analyzing light having spectral components periodic in frequency comprising: a. light conditioning means for collecting, collimating and transmitting said light; and b. primary interferometric means adapted to receive said light for selectively separating periodic spectra therefrom and transmitting said spectra in the form of a detectable signal, said primary interferometric means having interference producing means for providing a plurality of transmission windows regularly spaced in frequency, the frequency spacing between adjacent windows being adjusted to equal substantially the frequency difference between adjacent spectral components of the same periodic spectrum, and scanning means for causing the transmission peaks for adjacent orders to coincide with the spectral lines of the components, whereby said detectable signal is a fringe derived from a plurality of periodic spectral lines and haS an intensity substantially equal to their sum.

Claim 3

Apparatus for measuring rotational Raman spectra of gaseous material comprising: a. light source means for generating monochromatic light; b. projecting means for directing said monochromatic light through said gaseous material to produce scattered light having spectral components periodic in frequency; c. light conditioning means for collecting, collimating and transmitting said scattered light; d. primary interferometric means adapted to receive said scattered light for selectively separating periodic spectra therefrom and transmitting said spectra in the form of a detectable signal, said primary interferometric means having interference producing means for providing a plurality of transmission windows regularly spaced in frequency, the frequency spacing between adjacent windows being adjusted to equal substantially the frequency difference between adjacent spectral components of the same periodic spectrum, and scanning means for causing the transmission peaks for adjacent orders to coincide with the spectral lines of the components, whereby said detectable signal is a fringe derived from a plurality of periodic spectral lines and has an intensity substantially equal to their sum; and e. detecting means for indicating the intensity of said signal.

Claim 4

Apparatus for measuring rotational Raman spectra of gaseous material comprising: a. light source means for generating monochromatic light; b. projecting means for directing said monochromatic light through said gaseous material to produce scattered light having spectral components periodic in frequency; c. light conditioning means for collecting, collimating and transmitting said scattered light; d. primary interferometric means adapted to receive said scattered light for selectively separating periodic spectra therefrom and transmitting said spectra in the form of a detectable signal, said primary interferometric means having interference producing means for providing a plurality of transmission windows regularly spaced in frequency, the frequency spacing between adjacent windows being adjusted to equal substantially the frequency difference between adjacent spectral components of the same periodic spectrum, and scanning means for causing the transmission peaks for adjacent orders to coincide with the spectral lines of the components, whereby said detectable signal is a fringe derived from a plurality of periodic spectral lines and has an intensity substantially equal to their sum; and e. detecting means for indicating the intensity of said signal.

Claim 5

synchronous detection means for detecting the intensity variation of the fringe, whereby said fringe can be identified.

Claim 6

synchronous detection means for detecting the intensity variation of the fringe, whereby said fringe can be identified.

Claim 7

Apparatus for analyzing light having spectral components periodic in frequency, comprising: a. light conditioning means for collecting, collimating and transmitting said light; b. primary interferometric means adapted to receive said light for selectively separating periodic spectra therefrom and transmitting said spectra in the form of a detectable signal, said primary interferometric means having interference producing means for providing a plurality of transmission windows regularly spaced in frequency, the frequency spacing between adjacent windows being adjusted to equal substantially the frequency difference between adjacent spectral components of the same periodic spectrum, and scanning means for causing the transmission peaks for adjacent orders to coincide with the spectral lines of the components, whereby said detectable signal is a fringe derived from a plurality of periodic spectral lines and having an intensity substantially equal to their sum; c. signal conditioning means including:

Claim 8

Apparatus for analyzing light having spectral components periodic in frequency, comprising: a. light conditioning means for collecting, collimating and transmitting said light; b. primary interferometric means adapted to receive said light for selectively separating periodic spectra therefrom and transmitting said spectra in the form of a detectable signal, said primary interferometric means having interference producing means for providing a plurality of transmission windows regularly spaced in frequency, the frequency spacing between adjacent windows being adjusted to equal substantially the frequency difference between adjacent spectral components of the same periodic spectrum, and scanning means for causing the transmission peaks for adjacent orders to coincide with the spectral lines of the components, whereby said detectable signal is a fringe derived from a plurality of periodic spectral lines and having an intensity substantially equal to their sum; c. signal conditioning means including:

Claim 9

Apparatus as recited in claim 3 wherein said modulating means has a modulating range of about one-half the frequency width of said fringe.

Claim 10

Apparatus as recited in claim 3 including indicating and recording means for displaying said signal.

Claim 11

Apparatus as recited in claim 3 wherein said modulating means is a piezoelectric cylinder and said synchronous detection means is a phase sensitive detection system.

Claim 12

Apparatus as recited in claim 3 including secondary interferometric means in series with and between said light conditioning means and said primary interferometric means for receiving said light, selectively separating preselected spectra therefrom and sending said light devoid of said separated spectra to said primary interferometric means for receiving said light, selectively separating preselected spectra therefrom and sending said light devoid of said separated spectra to said primary interferometric means, said secondary interferometric means having interference producing means for providing a plurality of transmission windows regularly spaced in frequency, the frequency spacing between adjacent windows being adjusted to substantially equal the frequency difference between adjacent spectral components of the periodic spectrum for the preselEcted spectra, and scanning means for causing the transmission peaks for adjacent windows of said secondary interferometric means to coincide with the spectral lines of the latter components.

Claim 13

Apparatus for analyzing light having spectral components periodic in frequency, comprising: a. light conditioning means for collecting, collimating and transmitting said light; b. primary interferometric means adapted to receive said light for selectively separating periodic spectra therefrom and transmitting said spectra in the form of a detectable signal, said primary interferometric means having interference producing means for providing a plurality of transmission windows regularly spaced in frequency, the frequency spacing between adjacent windows being adjusted to equal substantially the frequency difference between spectral components of the same periodic spectrum, and scanning means for causing the transmission peaks for adjacent orders to coincide with the spectral lines of the components, whereby said detectable signal is a fringe derived from a plurality of periodic spectral lines and having an intensity substantially equal to their sum; and c. secondary interferometric means in series with and between said light conditioning means and said primary interferometric means for receiving said light, selectively separating preselected spectra therefrom and sending said light devoid of said separated spectra to said primary interferometric means, said secondary interferometric means having interference producing means for providing a plurality of transmission windows regularly spaced in frequency, the frequency spacing between adjacent windows of said interferometric means being adjusted to substantially equal the frequency difference between adjacent spectral components of the periodic spectrum for the preselected spectra and scanning means for causing the transmission peaks for adjacent orders of said secondary interferometric means to coincide with the spectral lines of latter components.

Claim 14

Apparatus for analyzing light having spectral components periodic in frequency, comprising: a. light conditioning means for collecting, collimating and transmitting said light; b. primary interferometric means adapted to receive said light for selectively separating periodic spectra therefrom and transmitting said spectra in the form of a detectable signal, said primary interferometric means having interference producing means for providing a plurality of transmission windows regularly spaced in frequency, the frequency spacing between adjacent windows being adjusted to equal substantially the frequency difference between spectral components of the same periodic spectrum, and scanning means for causing the transmission peaks for adjacent orders to coincide with the spectral lines of the components, whereby said detectable signal is a fringe derived from a plurality of periodic spectral lines and having an intensity substantially equal to their sum; and c. secondary interferometric means in series with and between said light conditioning means and said primary interferometric means for receiving said light, selectively separating preselected spectra therefrom and sending said light devoid of said separated spectra to said primary interferometric means, said secondary interferometric means having interference producing means for providing a plurality of transmission windows regularly spaced in frequency, the frequency spacing between adjacent windows of said interferometric means being adjusted to substantially equal the frequency difference between adjacent spectral components of the periodic spectrum for the preselected spectra and scanning means for causing the transmission peaks for adjacent orders of said secondary interferometric means to coincide with the spectral lines of latter components.

Claim 15

Apparatus as recited in claim 8 including multipass means for directing said detectable signal through said primary interferometric means, whereby the contrast ratio of said signal is increased.

Claim 16

Apparatus for analyzing light having spectral components periodic in frequency, comprising: a. light conditioning means for collecting, collimating and transmitting said light; b. primary interferometric means adapted to receive said light for selectively separating periodic spectra therefrom and transmitting said spectra in the form of a detectable signal, said primary interferometric means having interference-producing means for providing a plurality of transmission windows regularly spaced in frequency, the frequency spacing between adjacent windows being adjusted to substantially equal the frequency difference between spectral components of the same periodic spectrum, and scanning means for causing the transmission peaks for adjacent orders to coincide with the spectral lines of the components, whereby said detectable signal is a fringe derived from a plurality of periodic spectral lines and having an intensity substantially equal to their sum; c. multipass means for directing said detectable signal through said primary interferometric means whereby the contrast ratio of said signal is increased.

Claim 17

Apparatus for analyzing light having spectral components periodic in frequency, comprising: a. light conditioning means for collecting, collimating and transmitting said light; b. primary interferometric means adapted to receive said light for selectively separating periodic spectra therefrom and transmitting said spectra in the form of a detectable signal, said primary interferometric means having interference-producing means for providing a plurality of transmission windows regularly spaced in frequency, the frequency spacing between adjacent windows being adjusted to substantially equal the frequency difference between spectral components of the same periodic spectrum, and scanning means for causing the transmission peaks for adjacent orders to coincide with the spectral lines of the components, whereby said detectable signal is a fringe derived from a plurality of periodic spectral lines and having an intensity substantially equal to their sum; c. multipass means for directing said detectable signal through said primary interferometric means whereby the contrast ratio of said signal is increased.

Claim 18

Apparatus as recited in claim 10 wherein said multipass means is a corner cube prism.

Claim 19

Apparatus as recited in claim 10 including signal conditioning means comprising modulating means for modulating the phase difference between interfering rays of said light so as to vary the intensity of the fringe, the modulating range being no greater than the frequency spacing between adjacent orders, and phase sensitive detection means for detecting the intensity variation of the fringe, whereby said fringe can be identified.

Claim 20

Apparatus as recited in claim 2 wherein said light source means is provided with means for projecting light having a line width and frequency stability about equal to or less than the instrumental width of said primary interferometric means.

Claim 21

Apparatus as recited in claim 2 wherein said light source means is a pulsed laser.

Claim 22

Apparatus as recited in claim 14 wherein said laser is associated with a time gated electronic detection system having (1) means for measuring the time interval required to send a pulse from said laser into a sample of gaseous material and receive a return signal caused by light scattered therein and (2) means for measuring the amplitude of said return signal.

Claim 23

Apparatus as recited in claim 8 including detecting means associated with said secondary interferometric means for receiving therefrom a signal containing said preselected spectra and measuring the amplitude of said signal.

Claim 24

Apparatus as recited in claim 16 wherein said preselected spectra are the spectra produced by Raman scattering of a major constitutent of a gaseous material.

Claim 25

Apparatus as recited in claim 17 wherein said gaseous material is air.

Claim 26

Apparatus as recited in claim 2 wherein said light source means is adapted to project plane polarized light and said apparatus includes polarizing means for receiving said scattered light and transmitting the light to said interferometric means.

Claim 27

Apparatus as recited in claim 19 wherein said polarizing means is adapted to reduce the intensity of polarized Rayleigh scattered light to a degree described by the depolarization ratio thereof and to reduce the intensity of the Raman scattered light to a substantially smaller degree.

Claim 28

Apparatus as recited in claim 1 wherein said primary interferometric means is a solid etalon having temperature control means associated therewith for adjusting the optical path length thereof.

Claim 29

Apparatus as recited in claim 8 wherein at least one of said primary and secondary interferometric means is a solid etalon having temperature control means associated therewith for adjusting the optical path length thereof.

Claim 30

Apparatus as recited in claim 6 including means for applying to said cylinder a voltage having a square wave form, the limits of said voltage being adjusted so that the intensity of said fringe alternates between its maximum and minimum values, means for determining for each cycle of said voltage the difference in photon count between said maximum and minimum values of said fringe to produce a signal count, and means for accumulating said signal count for a preselected period of time over a preselected number of cycles of said square wave.

Claim 31

Apparatus as recited in claim 23 including means for varying the preselected time period and the preselected number of cycles inversely with the intensity of said fringe.

Claim 32

Apparatus as recited in claim 6 wherein said phase sensitive detection system is a lock in amplifier.

Claim 33

Apparatus as recited in claim 3 wherein said modulating means is a piezoelectric cylinder and said synchronous detection means is a photon counting system.

Claim 36

A method as recited in claim 27, including the steps of modulating the phase difference between interfEring rays of said light so as to vary the intensity of the fringe, the modulating range being no greater than the frequency spacing between adjacent orders, and detecting the intensity variation of the fringe.

Claim 37

A method as recited in claim 27 including the steps of selectively separating preselected spectra from said light and transmitting said light devoid of said separated spectra prior to the step of interferometrically separating periodic spectra from said light.