Optical range calculation apparatus and method of extending a measurable range

Abstract

An apparatus () comprises a light source that emits light modulated selectively at first and second modulation frequencies. A photonic mixer cell () generates and stores a plurality of electrical output signals respectively corresponding to phase offset values applied in accordance with an indirect time of flight technique and in respect of the selected modulation frequency. A signal processing circuit processes a first number of the electrical output signals at the first modulation frequency to calculate a first measurement phase angle (φ) from a calculated first measurement vector, and a second number of the electrical output signals at the second modulation frequency to calculate a second measurement phase angle (φ) from a second calculated measurement vector. A phase angle difference (Δφ) between the first and second measurement phase angles (φ, φ) is then calculated and a correction value (φ) applied to the phase angle difference (Δφ) to yield an extended range phase angle (φ) for calculating a range.