Inversion of Fabry-Perot CCD Images: A comparison of techniques

The Fabry-Perot interferometer has been used extensively to probe the upper atmosphere of the earth from ground based and satellite observatories. The high spectral resolution and throughput of this device make it ideal for measuring the line shapes and Doppler shifts of absorption and emission spectral features. Detectors for near visible Fabry-Perot interferometers have advanced from photographic film to single channel photomultipliers to multichannel photomultipliers. Further advances in our understanding of the physical processes dominating the upper atmosphere demand observational capability near 1µ. In the red and near-infrared portions of the spectrum, charge-coupled devices (CCD) are very efficient detectors. High quantum efficiency and broad spectral response (UV to near infrared) render CCDs highly desirable as imaging devices for Fabry-Perot interferometer applications. Other important characteristics of CCDs are their high spatial resolution, low noise, large dynamic range and linearity. A major limitation is the read noise, which restricts low light level applications unless special precautions are taken. This paper discusses one way to reduce the effect of read noise when the image is a circularly symmetric pattern such as a Fabry-Perot finge.