A rocket-borne spectroheliograph designed to take monochromatic pictures of the sun in the Mg II line at 2802.7 A is described in detail. The photographic system consists of a Questar telescope, a Solc type birefringent filter, and an automatic Robot camera. The double Solc filter has a spectral bandwidth of 3.5 A. The two units in the double filter have been thoroughly tested and are compared with theoretically calculated transmission curves. Two new types of linear film polarizers for the uv region have been tested and used in the filter. A temperature control unit was developed which stabilized the filter temperature in flight to within +/-0.2 degrees C. The instrument has been tested in vacuum and to the Aerobee 150 vibration specifications. It has been flown and successfully recovered three times and performed excellently during each fight.

Rocket spectroheliograph for the Mg II line at 2802.7 angstrom units.

This letter describes a tunable optical filter that couples light energy between ordinary and extraordinary polarizations in a birefringent electro‐optic crystal at the phase‐matched wavelength by means of a spatially periodic dc electric field. The specific embodiment described here is a LiTaO3 platelet operating with transverse electric field and located between cross polarizers. Analogies to both the Solc birefringent filter and the Harris acousto‐optic filter are cited. The electro‐optic filter is tuned by varying the spatial period of the electric field via an array of separately addressable finger electrodes. We have demonstrated tunability from 4700 A to 4.5 μm. Experimental results of transmittance versus applied voltage and of bandwidth versus pass wavelength agree well with theory. The flexibility of this type of electronic filter in allowing synthesis of arbitrary transfer functions through nonperiodic voltage distributions is emphasized.

V.I. Skomorovsky

Papers

Solc filter in optically active anisotropic crystal slabs