Described herein is a method and sensor of processing time-of-flight (TOF) signals in a TOF camera system including an illumination unit and an imaging sensor. The method comprises illuminating the scene with light at a first frequency, detecting reflected light from at least one object in the scene at the first frequency, and determining a phase measurement using I and Q values. In addition, the scene is illuminated with light at a second frequency, the second frequency being 2 -n of the first frequency where n=1, 2,..., etc., and the signs of I and Q values for both the first and second frequencies is used to determine the presence of aliasing in the phase measurement so that it can be corrected. The phase measurement is then corrected for aliasing and the effective range of the TOF camera system is extended by multiples of 2n. In addition, relative signal strength needs to be considered in accordance with the reflectivity of objects within the scene. For a reflectivity of 4% and no aliasing, the ability to detect an object decreases with distance (30). For an aliased phase measurement for an object with a reflectivity of 100%, the ability to detect the object is substantially constant (35).

Improvements in or relating to the processing of time-of-flight signals

Disclosed is a distance measuring apparatus which includes: a first pulse generating means (135) which generates reference signals; a second pulse generating means (137) which generates subject detection signals; a time measuring section (139) which measures a period of time from a time when a first pulse is generated to a time when a second pulse is generated; a first phase detecting section (141) which detects the first phase of a signal received using a signal at a first frequency; a second phase detecting section (163) which detects the second phase of a signal received using a signal at a second frequency; and a distance calculating section (165) which calculates the distance to the subject on the basis of output from the time measuring section, the first phase detecting section and the second phase detecting section.

Distance measuring apparatus and distance measuring method

PROBLEM TO BE SOLVED: To reduce the influence by reflection of range light by fine particles in air during long range measurement by a light wave range finder of a phase difference system. SOLUTION: This light wave range finder includes a light emitting element (11) emitting light modulated with a plurality of modulation frequencies (F 1 , F 2 and F 3 ), a light receiving element (30) receiving light emitted from the light emitting element, a plurality of frequency converters (32, 35 and 38) connected to the light receiving element, and a shutter (28) switching the light emitted from the light emitting element to a range measuring optical path through which the light reciprocates to a target reflective object and enters the light receiving element or a reference optical path through which the light passes inside the light wave range finder and enters the light receiving element. In the light wave range finder, local oscillation signals of different frequencies are added to the plurality of frequency converters, and the local oscillation signal of the lowest frequency (F 2 -F 3 +ΔF 3 ) has a frequency somewhat different from the difference (F 2 -F 3 ) between the second-lowest modulation frequency (F 2 ) and the lowest modulation frequency (F 3 ). COPYRIGHT: (C)2011,JPO&INPIT

Light wave range finder

PURPOSE:To reduce the error of measuring distance against the object, by reducing the error rate of the phase difference between the transmission wave and the reflective wave.

Taiji Hara

Papers

Distance measuring method and its device