  We designed, fabricated, and characterized four arrays of horn--coupled,
lumped element kinetic inductance detectors (LEKIDs), optimized to work in the
spectral bands of the balloon-borne OLIMPO experiment. OLIMPO is a 2.6 m
aperture telescope, aimed at spectroscopic measurements of the
Sunyaev-Zel'dovich (SZ) effect. OLIMPO will also validate the LEKID technology
in a representative space environment. The corrected focal plane is filled with
diffraction limited horn-coupled KID arrays, with 19, 37, 23, 41 active pixels
respectively at 150, 250, 350, and 460$\:$GHz. Here we report on the full
electrical and optical characterization performed on these detector arrays
before the flight. In a dark laboratory cryostat, we measured the resonator
electrical parameters, such as the quality factors and the electrical
responsivities, at a base temperature of 300$\:$mK. The measured average
resonator $Q$s are 1.7$\times{10^4}$, 7.0$\times{10^4}$, 1.0$\times{10^4}$, and
1.0$\times{10^4}$ for the 150, 250, 350, and 460$\:$GHz arrays, respectively.
The average electrical phase responsivities on resonance are 1.4$\:$rad/pW,
1.5$\:$rad/pW, 2.1$\:$rad/pW, and 2.1$\:$rad/pW; the electrical noise
equivalent powers are 45$\:\rm{aW/\sqrt{Hz}}$, 160$\:\rm{aW/\sqrt{Hz}}$,
80$\:\rm{aW/\sqrt{Hz}}$, and 140$\:\rm{aW/\sqrt{Hz}}$, at 12 Hz. In the OLIMPO
cryostat, we measured the optical properties, such as the noise equivalent
temperatures (NET) and the spectral responses. The measured NET$_{\rm RJ}$s are
$200\:\mu\rm{K\sqrt{s}}$, $240\:\mu\rm{K\sqrt{s}}$, $240\:\mu\rm{K\sqrt{s}}$,
and $\:340\mu\rm{K\sqrt{s}}$, at 12 Hz; under 78, 88, 92, and 90 mK
Rayleigh-Jeans blackbody load changes respectively for the 150, 250, 350, and
460 GHz arrays. The spectral responses were characterized with the OLIMPO
differential Fourier transform spectrometer (DFTS) up to THz frequencies, with
a resolution of 1.8 GHz.
