optical angle measuring apparatus, namely, autocollimators, autocollimation telescopes, goniometers, laser interferometers, tachymeters, theodolites, slope measuring deflectometry systems comprised of combination of collimator and telescope or angle measuring devices using the vignetting effect or using double pencil slope angle interferometers, angular encoders, clinometers, inclination measuring instruments, namely, surveyors' levels, and inclination measuring sensors; optical angle checkin...

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