An interferometer which may be used in a Fourier transform infra red spectrometer comprises a beam splitter (10), first and second fixed mirrors (18,26), path length variation means (20), and a folding mirror (16). The optical components are mounted on a casting (8) such that the beam splitter (10) and folding mirror (16) are arranged parallel to each other and the fixed mirrors (18,26) are attached to a single face of the casting in the same plane. The path length variation means (20) comprises two parallel opposed mirrors (22,24) which are rotatable to vary the length of the optical path between the beam splitter (10) and the fixed mirror (26).

An interferometric measurement system capable of measuring tilt of a reflecting surface with respect to a vertical axis. The system preferably includes four laser beams spaced at predetermined distances to measure distances between the measurement system and four locations on the reflecting surface. A controller is also provided for receiving inputs from the measuring laser beams to mathematically determine a tilt of the location being measured.

A focusing interferometer, wherein the focusing and orientation of the different mirrors of the interferometer have been successfully facilitated by combining the focusing mirror and the collimating mirror to provide a single spherical mirror surface and by reversing the paths of light that start from the beam splitter by assembly of mirrors which are arranged back-to-back to reflect to opposite directions such that their optical axes join, each of the mirrors including three flat mirror surfaces that are perpendicular to one another and are arranged to reflect to the direction of the point where the normals of the mirror surfaces intersect.

A scanning interferometer includes an optical arrangement. The optical arrangement therein includes two mirrors diverting the travel direction of light, arranged back-to-back such that they reflect to opposite directions and that their optical axes join. The mirrors are arranged in a mounting, which is arranged to move back and forth by a moving mechanism. The mounting includes a base element supported by the body of the interferometer, at least two support arms connected with the base element at their first ends via first bending points and a mounting element connected with the second ends of the support arms via second bending points, the mirrors being fastened to the mounting element. The mechanism moving the mounting includes a assembly generating a linear back-and-forth movement and a transmission mechanism for converting the back-and-forth movement to a back-and-forth movement of the mounting element.

A spectrometer (100) includes a light source (102) providing output light (106) to the bundled input ends (108) of multiple light pipes (110). The light pipes (110) branch into sets (118) between their input ends (108) and output ends (114), with each set (118) illuminating a sample detector (126) (via a sample chamber (122)) for measuring light scattered or emitted by a sample, or a reference detector (128) for obtaining a reference/datum measurement of the supplied light, so that comparison of measurements from the sample detector (126) and the reference detector (128) allows compensation of the sample detector measurements for drift. Efficient and accurate measurement is further assured by arraying the multiple light pipes (110) in each set (118) about the input bundle (116) so that each set receives at least substantially the same amount of light from the light source (102).