US 6,587,186 B2 · CMOS-compatible three-dimensional image sensing using reduced peak energy

Abstract

A three-dimensional time-of-flight (TOF) system includes a low power optical emitter whose idealized output S1=cos(ω·t) is reflected by a target distance z away as S2=A·cos(ω·t+Φ), for detection by a two-dimensional array of pixel detectors and associated narrow bandwidth detector electronics and processing circuitry preferably fabricated on a common CMOS IC. Phase shift Φ is proportional to TOF or z, z=Φ·C/2·ω=Φ·C/{2·(2·π·f)}, and A is brightness. Φ, z, and A are determined by homodyne-mixing S2 with an internally generated phase-delayed version of S1, whose phase is dynamically forced to match the phase of S2 by closed-loop feedback. Idealized mixer output per each pixel detector is 0.5·A·{cos(2ω·t+Φ)+cos(Φ)}. On-chip circuitry can use TOE data to simultaneously measure distance, object point velocity, object contours, including user interface with virtual input devices.

Claims20

Dependent claims

A method to determine distance z between a pixel detector and a target, the method comprising the following steps:

(a) illuminating said target with optical energy having a periodic waveform that includes a high frequency component S1(ω·t);
(b) disposing said pixel detector so as to detect an optical energy signal having a high frequency component S2(ω·t)=A·S1(ω·t−Φ) reflected from said target, where A is a coefficient proportional to brightness of said target, and Φ is phase shift proportional to time-of-flight of light over said distance z;
and
(c) homodyne signal-processing said signal S2(ω·t) to generate a phase signal Φ proportional to said distance z and to preserve said coefficient A;
wherein homodyne signal-processing at step (c) is carried out using an internally generated signal whose frequency is derived from said S1(ω·t) and whose phase is dynamically forced by closed loop feedback to track said high frequency component S2(ω·t).

2 more elements

Dependencies are inferred from the claim text.

CMOS-compatible three-dimensional image sensing using reduced peak energy

Life of this patent

CMOS-compatible three-dimensional image sensing using reduced peak energy

Life of this patent

Abstract

Claims20