Fourier spectrometer with exchangeable entrance and exit ports allowing for both internal and external radiation sources

An optical Fourier transform spectrometer comprising:

• a spectrometer housing having an exit;
• an internal radiation source disposed within the housing and producing an internal radiation beam;
• an interferometer disposed within the housing;
• an external radiation source disposed outside of the housing and producing an external radiation beam;
• detector means disposed within the housing;
• and
• optical guiding means comprising stationary optical element means and movable optical element means, the movable optical element means having a first and a second position to effect an optical path reversal in the Fourier transform spectrometer the movable optical element means, in the first position, guiding the internal radiation along a first optical path from the internal radiation source, through the interferometer, and through the exit out of the housing, the movable optical element means, in the second position, guiding the external radiation beam from the external radiation source through the exit into the housing, through the interferometer, and onto the detector means, wherein the first and second optical paths are reversed relative to another along a first and a second optical path segment, the first and the second optical path segments having a common contact point at which an optical element is located.

A method for operating a Fourier transform spectrometer, the spectrometer comprising a spectrometer housing having an exit, an internal radiation source disposed within the housing and producing an internal radiation beam, an interferometer disposed within the housing, an external radiation source disposed outside of the housing and producing an external radiation beam, detector means disposed within the housing, and optical guiding means comprising stationary optical element means and movable optical element means having a first and a second position, the method comprising the steps of:

• a) setting the movable optical element means to the first position;
• b) guiding, via the optical guiding means, the internal radiation along a first optical path from the internal radiation source, through the interferometer, and through the exit out of the housing;
• c) setting the movable optical element means to the second position;
• and
• d) guiding, via the optical guiding means, the external radiation along a second optical path from the second radiation source through the exit into the housing, through the interferometer, and onto the detector means.

A method for operating a Fourier transform spectrometer, the spectrometer comprising a spectrometer housing having an exit, an internal radiation source disposed within the housing and producing an internal radiation beam, an interferometer disposed within the housing, an external radiation source disposed outside of the housing and producing an external radiation beam, detector means disposed within the housing, optical guiding means comprising stationary optical element means and movable optical element means having a first and a second position, the method comprising the steps of:

• a) setting the movable Optical element means to the first position;
• b) guiding, via the optical guiding means, the internal radiation along a first optical path from the internal radiation source, through the interferometer, and through the exit out of the housing;
• c) setting the movable optical element means to the second position;
• and
• d) guiding, via the optical guiding means, the external radiation along a second optical path from the second radiation source through the exit into the housing, through the interferometer, and onto the defector means, the second optical path being reversed relative to the first optical path along first and second optical path segments having a common contact point at which an optical element is located.