  We have developed and characterized an imaging instrument to measure the
spatial properties of the diffuse near-infrared extragalactic background light
in a search for fluctuations from z > 6 galaxies during the epoch of
reionization. The instrument is part of the Cosmic Infrared Background
Experiment (CIBER), designed to observe the extragalactic background light
above the Earth's atmosphere during a suborbital sounding rocket flight. The
imaging instrument incorporates a 2x2 degree field of view, to measure
fluctuations over the predicted peak of the spatial power spectrum at 10
arcminutes, and 7"x7" pixels, to remove lower redshift galaxies to a depth
sufficient to reduce the low-redshift galaxy clustering foreground below
instrumental sensitivity. The imaging instrument employs two cameras with
\Delta \lambda / \lambda ~0.5 bandpasses centered at 1.1 and 1.6 microns to
spectrally discriminate reionization extragalactic background fluctuations from
local foreground fluctuations. CIBER operates at wavelengths where the
electromagnetic spectrum of the reionization extragalactic background is
thought to peak, and complements fluctuations measurements by AKARI and Spitzer
at longer wavelengths. We have characterized the instrument in the laboratory,
including measurements of the sensitivity, flat-field response, stray light
performance, and noise properties. Several modifications were made to the
instrument following a first flight in 2009 February. The instrument performed
to specifications in subsequent flights in 2010 July and 2012 March, and the
scientific data are now being analyzed.
