Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrometer
Patent
1990-11-02
1992-10-20
Turner, Samuel A.
Optics: measuring and testing
By dispersed light spectroscopy
Utilizing a spectrometer
356346, G01B 902
Patent
active
051574586
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a polarization interferometer which comprises a source of light, a collimator system for generating parallel light rays, a first polarizing means which polarizes the parallel light rays, a double-refractive element with at least two plane-parallel lateral surfaces being perpendicular to the polarized parallel light rays, and a second polarizing means which polarizes the light emerging from the double-refractive element and directs it to a photon detector.
BACKGROUND OF THE INVENTION
The most important and most frequently used interferometer is the Michelson one with its many modifications. The light of a mostly monochromatic light source is split up by a semitransparent, reflecting surface of an optical beamsplitter into two partial beams. After its reflection by two mirrors, the beamsplitter recombines both of them to a single light beam. This union leads to interference fringes whose contortion or displacement constitutes a measure for the difference of the optical paths between the two partial beams.
The known interferometers can be used for a great number of tasks, e.g. for:
The known interferometers, however, provide the following disadvantages: employed only for that light extending until the medium infrared range; for light in a more short-wave range there are considerable expenses for equipment; and moved, becomes indispensable.
The invention alleviates the foregoing problem. The invention has the basic task to provide a polarization interferometer differing from the conventional apparatuses in so far as: factor of one hundred as compared with the known Michelson arrangement, without increasing the expenses; and design which is relatively insensitive to vibrations.
SUMMARY OF THE INVENTION
The invention attains the desired aim by using a polarization interferometer of the kind described which is characterized in that the double-refractive element consists of two optical wedges displaceable along those lateral surfaces which face each other, said wedges complementing each other to a right parallelepiped, and of a double-refractive, plane-parallel plate serving as a compensator. The optical axis of the compensator is twisted in a plane perpendicular to the light beam by a finite angle relatively to that of the two wedges and the optical axes of the two wedges coincide with each other, while the optical axes of the two polarizers form an angle with one another the value of which is divisible by 90 degrees, i.e. they are perpendicular or parallel to each other.
The advantages obtained by the invention are essentially defined by the fact that, thanks to the polarization interferometer provided by the invention, the range of the measurable spectral region can be extended by at least a hundred times in relation to all known kinds of measurements applied in the field of Michelson interferometry measuring the displacement of the movable mirror as compared with the stationary mirror. Further, the optical construction units used in the interferometer provided by the invention have to meet far less severe requirements in regard of precision and planarity.
Contrary to the double-beam interferometer, the two parts of one and the same beam of light polarized perpendicularly to one another are brought to interference in the case of the interferometer according to the invention. This provides the advantage that even in case of image defects (e.g. by mechanical vibrations or imperfect driving mechanisms and guidances) the spatially lateral interference is entirely preserved since both polarizing components are conjugated at the same place. This particularly allows a far higher speed in carrying out the interferogram.
Due to its mechanical insensitivity to ambient conditions and the low testing time, the polarization interferometer in accordance with the invention particularly applies--besides its previously mentioned uses--to routine analysis in laboratories and industrial enterprises; taking up the spectrum in the near infrared wave range makes it possible, by
REFERENCES:
patent: 3737235 (1973-06-01), Hawes
patent: 4320973 (1982-03-01), Fortunato et al.
patent: 4732482 (1988-03-01), Rippel
patent: 5013153 (1991-05-01), Disch et al.
Glaus Ulrich
Labhart Martin
Wagner Heinz
Bran & Luebbe GmbH
Buhler AG
Farber Martin A.
Turner Samuel A.
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