integral field spectrograph

An integral field spectrograph (or integral field spectrometer) combines spectrography and imaging, producing a "cube" of data (three dimensions), two being spatial (the image) and one being the spectral data at each specified point. Its use is called integral field spectroscopy (IFS).

It is commonly a "normal" spectrograph plus an integral field unit (IFU). A "normal" spectrograph collects data from a narrow line-like area rather than from a two-dimensional area, offering spectral data over one spatial dimension. The integral field unit rearranges points of light so that the slit includes data across a two-dimensional area, paying for this capability by lowering the spatial resolution. Spectrographs are often built so they can be used with or without the integral field unit.

Methods used:

• Image slicer directs light from different parts of the image into a slit such that parts of the image across two dimensions are all fed through the one dimension of the slit width. UVES of the ESO VLT does this.
• Lenslet array has a lens for each pixel. SAURON of the William Herschel Telescope (WHT) uses this.
• Fibers uses optical fibers to direct the image into a single slit. INTEGRAL, used on the WHT uses this.