Indirect time of flight range calculation apparatus and method of calculating a phase angle in accordance with an indirect time of flight range calculation technique

Abstract

An indirect time of flight range calculation apparatus (100) comprises a light source, a photonic mixer cell (102) that generates a plurality of output signals respectively corresponding to a first plurality of predetermined phase values (p1, p2, . . . , pm). A signal processing circuit (110, 124, 128, 146) is also provided to process the first plurality of electrical output signals in order to calculate a first vector and a first angle from the first vector. The photonic mixer (102) generates a second plurality of electrical output signals corresponding to a second plurality of predetermined phase values ([p1, p2, . . . , pm]+Pi / m). Each phase value of the second plurality of predetermined phase values is respectively offset with respect to each phase value of the first plurality of predetermined phase values by a predetermined phase offset value. The signal processing circuit (110, 124, 128, 146) processes the second plurality of electrical output signals in order to calculate a second vector, and de-rotates the second vector calculated and calculate a second angle from the de-rotated second vector before offsetting the second angle against the first angle, thereby generating a corrected output angle, which is used to calculate a range.

Description

technical field [0001] The present invention relates to an indirect time-of-flight distance calculation device of the type that uses phase delays to index measurements, for example. The invention also relates to a method of calculating the phase angle according to the indirect time-of-flight technique, of the type, for example, using a phase delay to index the measurement. Background technique [0002] In so-called time-of-flight sensing systems and other systems (such as game console vision systems), it is known to employ an illumination source to illuminate the surrounding environment (sometimes referred to as a "scene") within the illumination source's field of view, and to process Light reflected by features of this scene. Such so-called LiDAR (Light Detection and Ranging) systems use an illumination source to illuminate a scene with light, and a detection device (such as a photodiode array, some optical elements and a processing unit) to detect the light reflected from...

AI Technical Summary

Problems solved by technology

[0009] However, any difference in amplitude, whether caused by amplitude circle error or by amplitude fluctuations between measurements, directly affects the accuracy of the extracted phase angle

[0010] Additionally, in this method, the number of phase samples to be obtained is overall 2×m, and while the distance and angle measurement accuracy is equal to that obtained by performing 2×m phase samples consecutively for one distance and angle measurement (accuracy ), but the obvious benefit of achieving performance similar to that of a sampled system is that, for example, doubling the sample size cannot be achieved without doubling the number of samples taken by the system, since in practice the above paper proposes an 8-phase sampling system

Moreover, the method is susceptible to so-called "ghost" images, in which moving objects or parts thereof may appear in different positions in the scene between the first and second measurements

Images