HAL Id: jpa-00213242
https://hal.archives-ouvertes.fr/jpa-00213242
Submitted on 1 Jan 1967HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci-entific research documents, whether they are pub-lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
AUTOMATIC CONTROL OF FABRY PEROT
INTERFEROMETERS
J. Ramsay
To cite this version:
JOURNAL DE PHYSIQUE Colloque C 2, supplkment au no 3-4, Tome 28, mars-Avril1967, page C 2
-
321AUTOMATIC CONTROL OF FABRY PEROT INTERFEROMETERS
Division of Physics, National Standards Laboratory, C . S. I. R. Q., Sydney, Australia.
The availability of interferometer plates of 75 mm diameter with errors in flatness less than 1/100 [I] raises the issue of very precise control of Fabry Perot interferometers in order to realize the full potentia- lities of these plates. There are essentially two para- meters to be controlled ; these are the parallelism and spacing of the plates.
A method of automatically controlling the parallelism of interferometers has been described earlier [2] [3].
To control the spacing a suitable reference scale must be established. One such scale is a monochro- matic beam of known wavelength. However, this method is usually too restrictive and too unreliable. A more satisfactory method for general purposes uses a dimensionally stable wedge-shaped reference interferometer as a scale. The spacing of the plates of the main interferometer is controlled to be the same as the spacing of a particular aperture in the wedge-shaped reference interferometer using super- position fringes. By appropriate selection of the aperture of the reference interferometer the main interferometer can be tuned to transmit any wave- length less than a predetermined maximum, which is set during manufacture. Details of the design, cons- truction and performance of an interferometer controlled for parallelism and spacing are described in a paper in Appl. Optics [4].
tically controlled as described above is to tune the reference interferometers by variation in pressure of the air between their surfaces. In operation the proce- dure would be as follows. The reference interferometer associated witch each main interferometer is mounted in a pressure enclosure each of which is connected to a common pressure tank. A monochromatic beam (e. g., from a He/Ne laser) is incident on the working apertures of the main interferometers. By rotation of their associated reference interferometers the working apertures are tuned to transmit a maximum. After this has been done the multiple interferometers can then be tuned synchronously by variation of the gas pressure in the reference interferometers. For the applications which I have in mind (the use of multiple interferometers as narrow band filters for solar research), tuning over approximately 100 band-widths is adequate : for resolving powers of lo4 or more a variation in pressure of approximately 4 atmospheres is required which is not unduly difficult.
Acknowledgements
-
The assistance of H. Kobler and E. G. V. Mugridge is gratefully acknowledged. This project has been sponsored in part by the Natio- nal Aeronautics and Space Administration of the U. S. A. under Contract No. N. A. S. r-208.REFERENCES It is very often necessary to use a series of interfe-
[ I ] G. OTTE J. Sci. Instrum., 1965, 42, 91 1.
rometers to achieve a desired result. A possible [21
J. V. RAMSAY, Appl. Optics, 1962, 411.
method of s ~ n c h r o n o u s l ~ tuning simultaneousl~ a [3] H. KOBLER, PJTOC. I. R. E. (Aust.), 1963, 24, 677. number of interferometers each of which is automa- [4] J. V. RAMSAY, Appl. Optics, 1966, 5 , 1291.
