Time of flight detection systems with efficient phase measurement

A distance measurement device comprising:

• an emitter (115) configured to emit a modulated waveform (120) in at least one predetermined drive frequency;
• a monitoring photodiode (225) configured to generate a reference signal in response to measuring the emitted modulated waveform;
• a receiver (130) configured to generate a received signal in response to a received waveform (125), wherein the received waveform comprises a reflection of the emitted modulated waveform;
• at least one analog-to-digital converter (ADC) (230) configured to digitize the reference signal and the received signal;
• and,
• a processing circuit (135) configured to determine a distance between the emitter and a target surface by distance determination operations (1500), the operations comprising:
• generate a pre-averaged received signal by averaging across multiple ADC samples of the received signal, and,
• determine a phase offset using a first digital single frequency analysis of the pre-averaged received signal, and a second digital single frequency analysis of the ADC samples of the reference signal, wherein the first and the second digital single frequency analyses are each performed at the predetermined drive frequency of the modulated waveform.

A method of indirect time-of-flight distance measurement comprising:

• emit a first modulated signal at a first predetermined modulation frequency;
• receive a first measured ADC sample of the first modulated signal;
• emit a second modulated signal at a second predetermined modulation frequency;
• receive a second measured ADC sample of the second emitted modulated signal;
• determine an averaged emitter ADC sample based on the first measured ADC sample and the second ADC sample;
• receive a third measured ADC sample of a first received signal, wherein the first received signal is generated based on a measured reflected signal of the first modulated signal from a target object;
• receive a fourth measured ADC sample of a second received signal, wherein the second received signal is generated based on a measured reflected signal of the second modulated signal from a target object;
• apply an output gain to the third measured ADC sample and the fourth ADC sample such that the noise to signal ratio is reduced;
• determine an averaged receiver ADC sample based on the third measured ADC sample and the fourth ADC sample;
• determine a received signal phase based on the averaged receiver ADC sample using a first single frequency digital analysis, and determine an emitter signal phase based on the averaged emitter ADC sample using a second single frequency digital analysis;
• and,
• determine a distance measurement as a function of the received signal phase and the emitter signal phase.