Mattson Instruments, Inc.

Analytical Technology, Inc.

David R Mattson

Stephen C Weibel

Joel P Covey

Scott A Callaghan

Randolph W Bach

A Fourier-transform (FT) infrared (IR) spectrometer includes a Michelson interferometer without an IR beam compensator. An input IR beam is directed through a substrate and a beamsplitter attached to the substrate for support, with the input IR beam divided by the beamsplitter into a first beam portion incident upon a fixed retroreflector and a second beam portion incident upon a movable retroreflector. The first and second beam portions are then recombined to provide an uncompensated output IR beam with an interference pattern which is directed onto a sample to provide an uncompensated interferogram. The uncompensated interferogram is converted from a time domain to a frequency domain via a Fourier-transform to provide a complex intermediate spectrum, followed by a calculation of a corrected phase angle in terms of wavenumber arising from the substrate's optical thickness. The complex intermediate spectrum is then rotated by a negative of the corrected phase angle. An inverse Fourier-transform is used to form a corrected real compensated intermediate interferogram. The corrected real compensated intermediate interferogram is then Fourier-transformed into a spectrum using a conventional approach to remove asymmetric noise and correct for small phase errors.

Apparatus and method for FTIR spectrometer without compensator

An interferometer including a beamsplitter and fixed and movable cube corner reflectors is adapted for use in a Fourier-transform infrared (FTIR) spectrometer. The spectrometer includes a cast metal base, such as of aluminum, with the interferometer including an IR source housing formed integrally with the base for dissipating heat via conduction. The IR source housing is hollow and open at the top for receiving a removable opaque printed circuit board (PCB) which is coupled to and provides support for and electrical current to an IR source within the housing. The housing includes two apertures in lateral portions thereof. An IR beam is directed by the source through a first aperture to the Michelson interferometer, while a second aperture is adapted to receive a fiber optic light guide to allow for direct viewing of the IR source in a safe manner without removing the PCB cover of the housing. An interferometer chamber is isolated from a sample chamber, both of which chambers may be independently purged and are further isolated from the spectrometer's electronic circuitry. The spectrometer includes a minimum number of reflectors outside of the interferometer for reduced light loss and improved signal-to-noise ratio with the interferometer providing an output IR beam to a first focus mirror which horizontally focuses the beam on and directs the beam through the sample and thence onto a second focus mirror which vertically focuses the beam on a closely spaced IR detector integrated in a printed circuit board.

Spectrometer and IR source therefor

A dual beam Fourier transform spectrometer produces two beams from a single infrared (IR) source. The beams are directed through a sample region, with one beam transiting a sample and the other beam transiting a reference cell. The sample and reference beams are then directed to a Michelson interferometer with cube corner retroflectors for optically cancelling the background signal from the separate sample and reference beams and for optically combining the sample and reference beams in an optically accurate and stable manner. The single combined beam, which contains the difference interferogram is directed to a single detector.

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Madison, WI, United States of America

David R Mattson