integral field unit
(instrument to allow a spectrograph to capture data over a 2D field)
An integral field unit (IFU) is an instrument that allows
a "normal" spectrograph, i.e., with a slit opening,
to capture data across a two-dimensional field.
The combined instrument is called an integral field spectrograph.
A typical spectrograph collects data from a line through
an image (one dimension) and offers 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, but at a relatively low
spatial resolution. Spectrographs are often built
so they can be used with or without the integral field unit.
Among the mechanisms used:
- An 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.
- A 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, another IFU for WHT, uses this.
The phrases IFU observation and IFU spectroscopy naturally refer to a
spectrographic observation using an IFU.
Referenced by pages:
Anglo-Australian Telescope (AAT)
Giant Magellan Telescope (GMT)
imaging Fourier transform spectroscopy (IFTS)
integral field spectrograph
William Herschel Telescope (WHT)
WIYN 3.5m Telescope