Phase anti-aliasing using spread-spectrum techniques in an optical distance measurement system

A transmitter for an optical distance measuring system, comprising:

• a signal generator configured to generate an electrical transmit signal at a plurality of frequencies over an integration time period, each of the plurality of frequencies depending on a length of one of a plurality of exposure time periods of a receiver;
• a light source configured to generate a transmit optical waveform corresponding with the electrical transmit signal;
• and
• an illumination driver coupled to the signal generator and the light source, the illumination driver configured to drive the light source;
• wherein the signal generator includes a first phased-lock loop (PLL), a second PLL, a frequency sequencer, and a multiplexer;
• wherein, during a first of the plurality of exposure time periods:
• the first PLL is configured to generate a first discrete electrical signal of the electrical transmit signal at a first frequency in the plurality of frequencies;
• the second PLL is configured to generate a second discrete electrical signal of the electrical transmit signal at a second frequency in the plurality of frequencies;
• and
• the multiplexer is configured to select the first discrete signal to drive the light source.

A method of determining a distance to an object, comprising:

• receiving, by a receiver, a reflected optical waveform that is a transmitted optical waveform reflected off of a target object;
• integrating the reflected optical waveform over an integration time period, the integration time period including a plurality of exposure time periods, a length of each of the plurality of exposure time periods depending on one of a plurality of frequencies of the transmitted optical waveform;
• and
• determining a distance to the target object based on a time of flight (TOF) of the transmitted optical waveform from a transmitter to the target object and back to the receiver as the reflected optical waveform, the TOF determined based on a correlation of an electrical transmit signal and the return optical waveform utilizing a correlation function with respect to the integration time period;
• wherein each of the plurality of exposure time periods depends on spectral power of the transmit optical waveform at a point in time within the integration time period.