  The Allen Telescope Array (ATA) is a cm-wave interferometer in California,
comprising 42 antenna elements with 6-m diameter dishes. We characterize the
antenna optical accuracy using two-antenna interferometry and radio holography.
The distortion of each telescope relative to the average is small, with RMS
differences of 1 percent of beam peak value. Holography provides images of dish
illumination pattern, allowing characterization of as-built mirror surfaces.
The ATA dishes can experience mm-scale distortions across -2 meter lengths due
to mounting stresses or solar radiation. Experimental RMS errors are 0.7 mm at
night and 3 mm under worst case solar illumination. For frequencies 4, 10, and
15 GHz, the nighttime values indicate sensitivity losses of 1, 10 and 20
percent, respectively. The ATA.s exceptional wide-bandwidth permits
observations over a continuous range 0.5 to 11.2 GHz, and future retrofits may
increase this range to 15 GHz. Beam patterns show a slowly varying focus
frequency dependence. We probe the antenna optical gain and beam pattern
stability as a function of focus and observation frequency, concluding that ATA
can produce high fidelity images over a decade of simultaneous observation
frequencies. In the day, the antenna sensitivity and pointing accuracy are
affected. We find that at frequencies greater than 5 GHz, daytime observations
greater than 5 GHz will suffer some sensitivity loss and it may be necessary to
make antenna pointing corrections on a 1 to 2 hourly basis.
