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Chapter 12:
An Imaging Fourier Transform Spectrometer
The Michelson, or maybe the Twyman-Green, interferometer can be converted to an imaging spectrometer by the simple addition of an array of detectors at the focal plane. 12.1 Monochromatic Operation Figure 12.1 shows the FTS device in an imaging mode. The front-end optical system (shown as a single lens on the left), generates a collimated beam that passes through the interferometer and covers a finite field of view. The full field of view depends on the size of the FPA that constitutes the field stop. The optics, which may be refractive or reflective, must cover the field with sufficient spatial resolution. The dashed lines show how an off-axis field point sends collimated beams through the interferometer on paths that are not parallel to the axis. These also demonstrate one of the design considerations of the imaging Michelson: the mirrors and beamsplitter must be large enough to accommodate the angles. It is also obvious that the beams do not return upon themselves from the two mirrors as they do with an on-axis ray.
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