Astronomical Optical Interferometry

A Literature Review by Bob Tubbs

St John's College Cambridge

Abstract

This report documents the development of optical interferometry and provides a physical explanation of the processes involved. It is based upon scientific papers published over the last 150 years, and I have included references to the ones which are most relevant. The reader is assumed to have an understanding of modern optical theory up to undergraduate level - References 28 and 29 give explanations at a more basic level. The formation of images from interferometric measurements is discussed and several example images are included.

Introduction

Fizeau first suggested that optical interferometry might be used for the measurement of stellar diameters at the Academie des Sciences in 1867. The short wavelength of light and the absence of sensitive calibrated detectors precluded more sophisticated interferometric measurements in the optical spectrum for over a century. After the Second World War most researchers instead turned to the radio spectrum, where macroscopic wavelengths and electronic detection greatly simplified the measurement of interferometric quantities. Modern computers, lasers, optical detectors and the data processing techniques developed for radio interferometry have recently enabled astronomers to produce high resolution images with optical arrays. At present only a few optical interferometer arrays are capable of image formation but many more are planned or under construction. The basic principles underlying the operation of optical interferometers have not changed, so I begin with a look at some of the earliest instruments.

Notes:

• Superscript numbers 1) link to the References section of this report and relate to relevant reference numbers.
• All unusual symbols are presented as GIF images.

For a more detailed description of astronomical optical interferometry I would recommend this review article by John Monnier (68 pages).