Method and apparatus for determining the wavelength of a light beam are provided. An input light beam is received, and light from the input light beam is distributed to multiple channels. At a first pair of interferometer cavities that has a first free spectral range, two of the multiple channels of light are received. The intensity of light reflected from the first pair of cavities is measured, and a first estimate of the wavelength or optical frequency of the input light beam is determined based on measurements of interference signals from the first pair of cavities and an initial estimate of the wavelength or optical frequency. At a second pair of cavities that has a second free spectral range smaller than the first free spectral range, another two of the multiple channels of light are received. The intensity of light from the second pair of cavities is measured, and a second estimate of the wavelength or optical frequency of the input light beam is determined based on the first estimate and measurements of interference signals from the second pair of cavities, in which the second estimate is more accurate than the first estimate.

A Fourier spectroscopic analyzer includes: a light receiver that receives a first wavelength component of a first wavelength band and a second wavelength component of a second wavelength band different from the first wavelength band, emits an interferogram to a sample, and outputs a first light reception signal acquired by receiving the first wavelength component and a second light reception signal acquired by receiving the second wavelength component; and a signal processing device that eliminates noise of the first wavelength component and acquires the spectrum by Fourier transform processing using the first light reception signal and the second light reception signal. The first wavelength band is a wavelength band of which a spectrum is acquired among wavelength components included in light that has passed through the sample. The interferogram is interference light and the sample is an analysis target.

An embodiment of a ruggedized interferometer is described that comprises a light source that generates a beam of light; a fixed mirror; a moving mirror that travels along a linear path; a beam splitter that directs a first portion of the beam of light to the fixed mirror and a second portion of the beam of light to the moving mirror, wherein the beam splitter recombines the first portion reflected from the fixed mirror and the second portion reflected from the moving mirror; and a servo control that applies a substantial degree of force to the moving mirror at initiation of a turnaround period, wherein the substantial degree of force is sufficient to redirect the moving mirror traveling at a high velocity to an opposite direction of travel on the linear path.

The Fourier transform infrared spectrophotometer includes: a light source 11 for generating infrared light having a wavelength width including an absorption wavelength of a compound to be analyzed; an interferometer including a fixed mirror 15 and a movable mirror 16, for generating interfering light from the infrared light; a detector 25 for generating a voltage with a magnitude corresponding to the intensity of the interfering light, and for outputting a voltage obtained by subtracting, from the aforementioned voltage, a voltage with a predetermined magnitude; a high-pass filter 464 for allowing the passage of frequency components equal to or higher than a predetermined frequency in an output voltage from the detector 25; an amplifier 463 for amplifying an output voltage from the high-pass filter 464 by a predetermined multiplying factor; and an analogue-to-digital converter 27 for converting an output voltage from the amplifier 463 into a digital signal.

[Object] The object of the invention is to present a new spectral measurement technique enabling a measurement even if light to be measured exists within a very short period.

[Means for Solution] A broadband pulsed light wave L1 where wavelength shifts temporally and continuously in a pulse interferes with a light wave L0 to be measured. The intensity at each wavelength of the light wave L0 to measured is obtained by the Fourier transform of the output signal from a detector 5 that has detected the intensity of the wave resultant from the interference. A laser beam L2 from a laser source 1 is converted to a supercontinuum wave L3 by a nonlinear optical element 2. A pulse extension element 3 extends pulses of the supercontinuum wave L3, thus generating the broadband pulsed light wave L1.

Method and apparatus for determining the wavelength of a light beam are provided. An input light beam is received, and light from the input light beam is distributed to multiple channels. At a first pair of interferometer cavities that has a first free spectral range, two of the multiple channels of light are received. The intensity of light reflected from the first pair of cavities is measured, and a first estimate of the wavelength or optical frequency of the input light beam is determined based on measurements of interference signals from the first pair of cavities and an initial estimate of the wavelength or optical frequency. At a second pair of cavities that has a second free spectral range smaller than the first free spectral range, another two of the multiple channels of light are received. The intensity of light from the second pair of cavities is measured, and a second estimate of the wavelength or optical frequency of the input light beam is determined based on the first estimate and measurements of interference signals from the second pair of cavities, in which the second estimate is more accurate than the first estimate.

The present invention belongs to the field of optical technology, disclosing a quadrilateral common-path time-modulated interferometric spectral imaging device and method. The present invention sets up a moving mirror scanning mechanism in a quadrilateral common path interferometer for generating optical path differences that vary with time, so that the quadrilateral common-path time-modulated interferometric spectral imaging device operates in the staring observation mode. The invention can make the quadrilateral common-path time-modulated interferometric spectral imaging device not only retain the advantages of common optical path spectroscopic technology, but also obtain high spectral resolution.

A full-range imaging method doubles imaging range of conventional techniques by removing mirror images of an imaged object that limit conventional images to a half-range and that are caused in part by the loss of phase information in a detected signal. Phase information of the detected signal is reconstructed with an averaging technique based on a modulated phase induced in the detected signal during scanning.

The Fourier transform infrared spectrophotometer includes: a light source 11 for generating infrared light having a wavelength width including an absorption wavelength of a compound to be analyzed; an interferometer including a fixed mirror 15 and a movable mirror 16, for generating interfering light from the infrared light; a detector 25 for generating a voltage with a magnitude corresponding to the intensity of the interfering light, and for outputting a voltage obtained by subtracting, from the aforementioned voltage, a voltage with a predetermined magnitude; a high-pass filter 464 for allowing the passage of frequency components equal to or higher than a predetermined frequency in an output voltage from the detector 25; an amplifier 463 for amplifying an output voltage from the high-pass filter 464 by a predetermined multiplying factor; and an analogue-to-digital converter 27 for converting an output voltage from the amplifier 463 into a digital signal.

A method for characterizing a light beam includes separating the light beam by a separator optic into first and second sub-beams; propagating the first and second sub-beams over first and second optics, respectively, said first and second optics being respectively arranged so that the sub-beams on leaving the optics are separated by a time delay ?; recombining the sub-beams so that they spatially interfere and form a two-dimensional interference pattern; measuring the frequency spectrum of at least part of the interference pattern; calculating the Fourier transform in the time domain of at least one spatial point of the frequency spectrum, the Fourier transform in the time domain having a time central peak and first and second time side peaks; calculating the Fourier transform in the frequency domain for one of the side peaks; calculating the spectral amplitude A.sub.R(?) and the spatial-spectral phase ?.sub.R(x,y,?) for the Fourier transform in the frequency domain.