Measurement system, measurement method, and non transitory computer readable storage medium

A measurement method to measure a distance to and a relative speed of targets, the measurement method comprising:

• outputting, toward the targets, a transmission light including a subcarrier in which a frequency is changed by modulating a carrier wave of a single frequency light source,
• performing a coherent detection on a reception light, which includes an in-phase component and an orthogonal component, and is reflected by and received from the targets, and detecting a difference regarding an amplitude and a phase between the reception light and a reference light from the transmission light including the subcarrier,
• performing Fast Fourier Transform (FFT) processing on a signal, which is generated based on both of the in-phase component and the orthogonal component of the reception light, and determining, as a first result, a peak by a first result acquisition unit;
• determining, as a second result, a peak frequency detected by performing FFT processing on at least one of the in-phase component signal and the orthogonal component signal by a second result acquisition unit;
• and
• determining, as a third result, a correspondence between the distance and the relative speed of a same target of the targets based on both of the first result and the second result by a combination determination unit.

A non-transitory computer readable storage medium comprising instructions for execution by a computer for a measurement system configured to measure a distance to and a relative speed of targets, the instructions causing at least one processors to implement:

• outputting, toward the targets, a transmission light including a subcarrier in which frequency is changed by modulating a carrier wave of a single frequency light source,
• performing a coherent detection on a reception light, which includes an in-phase component and an orthogonal component, and is reflected by and received from the targets, and detecting a difference regarding an amplitude and a phase between the reception light and a reference light from the transmission light including the subcarrier,
• performing Fast Fourier Transform (FFT) processing on a signal, which is generated based on both of the in-phase component and the orthogonal component of the reception light, and determining, as a first result, a peak;
• determining, as a second result, a peak frequency detected by performing FFT processing on at least one of the in-phase component signal and the orthogonal component signal;
• and
• determining, as a third result, a correspondence between the distance and the relative speed of a same target of the targets based on both of the first result and the second result.

A measurement system comprising:

• a laser configured to output a carrier wave as a single frequency light source;
• a modulator configured to generate a transmission light having a subcarrier by modulating the carrier wave and output the transmission light toward a plurality of targets;
• a coherent detector configured to receive a reception light reflected by and received from the plurality of targets, the reception light including an in-phase component and an orthogonal component, receive a reference light from the transmission light including the subcarrier, and detect a difference regarding an amplitude and a phase between the reception light and the reference light;
• and
• a measurement device comprising:
• a digital signal processor configured to:
• perform Fast Fourier Transform (FFT) processing on a signal generated based on both of the in-phase component and the orthogonal component of the reception light,
• determine, as a first result, a plurality of peak frequencies regarding a distance and a plurality of peak frequencies regarding a relative speed, each peak frequency regarding the distance and each peak frequency regarding the relative speed corresponding to a respective target of the plurality of targets;
• determine, as a second result, a peak frequency detected by performing FFT processing on at least one of spectra of the in-phase component signal and spectra of the orthogonal component signal;
• and
• determine, as a third result, for each target of the plurality of targets, a correspondence between one of the plurality of peak frequencies regarding the distance and one of the plurality of peak frequencies regarding the relative speed, based on both of the first result and the second result.