Circle to line interferometer optical system

This study describes a technique and apparatus for converting the circular fringes of a Fabry-Perot interferometer into a linear pattern which can be detected with a conventional linear detector. The conversion from a circular ring pattern at the focus of the objective lens of the interferometer is accomplished using a segment of an internally reflecting cone to direct the light from a sector of the ring pattern onto the linear detector. Light is concentrated into a single sector by the use of a kaleidoscopic mirror system. The aberrations associated with the transformation are shown to be small for high resolution devices which have large F numbers. A laboratory demonstration of a linearly scanned Fabry-Perot interferometer with a 0.7 cm. spacing illustrates a spectrum taken over ten orders with very small aperture defects. These results imply that a high resolution interferometer using five orders and a CCD detector would have a sensitivity 87.5 x greater than is presently achieved with those used to observe the winds in the upper atmosphere.