Two frequency time-of-flight three-dimensional image sensor and method of measuring object depth

A three-dimensional image (3DI) system comprising:

• a modulator configured to generate a first modulation signal having a first modulation frequency and a second modulation signal having a second modulation frequency;
• an illumination source configured to generate a modulated light signal based on the first modulation signal;
• a sensor core including a pixel array modulated by the second modulation signal, wherein at least one pixel of the pixel array is configured to receive the modulated light signal reflected from an object as a reflected modulated light signal and to demodulate the reflected modulated light signal using the second modulation signal during an image acquisition to generate a measurement signal, wherein the at least one pixel is configured to generate a plurality of measurement signals based on a plurality of image acquisitions taken at different acquisition times;
• and
• a control unit including at least one processor, the control unit configured to:
• control a phase difference between the first modulation signal and the second modulation signal by setting the first modulation frequency and the second modulation frequency to have a predetermined frequency difference greater than zero;
• control the sensor core to initiate the plurality of image acquisitions at the different acquisition times;
• receive the plurality of measurement signals, and
• calculate a depth of the object based on the plurality of measurement signals, wherein the depth is a distance from the 3DI system to the object.