Dual-beam fmcw distance measuring method having compensation of a velocity-dependent distance measurement error

A distance measuring method comprising:

• generating a first and a second laser radiation, wherein
• the first laser radiation comprises a first frequency modulation defining a first modulation band, and
• the second laser radiation comprises a second frequency modulation defining a second modulation band, wherein a gradient of the first frequency modulation is different from a gradient of the second frequency modulation in at least some time intervals;
• simultaneously emitting at least a part of the first laser radiation and at least a part of the second laser radiation as the first or as the second emission radiation, respectively, toward the target;
• receiving at least a part of the first emission radiation returning from the target and at least a part of the second emission radiation returning from the target as the first or as the second reception radiation, respectively;
• generating a first and a second mixed signal based on a mixture of the first reception radiation with a first local oscillator radiation or based on a mixture of the second reception radiation with a second local oscillator radiation, respectively, for a distance measurement according to the principle of a frequency-modulated continuous wave radar;
• and
• determining at least one distance to the target based on the first and the second mixed signal,
• wherein:
• a parameter is determined, which is indicative of a frequency offset between the first and the second modulation band, and
• the parameter is taken into consideration during the determination of the at least one distance to the target to derive a frequency difference between the first frequency modulation and the second frequency modulation.

A distance meter comprising:

• a laser radiation source configured for generating a first and a second laser radiation, wherein:
• the first laser radiation comprises a first frequency modulation defining a first modulation band, and
• the second laser radiation comprises a second frequency modulation defining a second modulation band, wherein a gradient of the first frequency modulation is different from a gradient of the second frequency modulation in at least some time intervals,
• i. an emission path configured for simultaneously emitting at least a part of the first laser radiation and at least a part of the second laser radiation as the first or as the second emission radiation, respectively, toward the target,
• ii. a receiver configured for receiving at least a part of the first emission radiation returning from the target and at least a part of the second emission radiation returning from the target as the first or as the second reception radiation, respectively,
• iii. a mixer configured for generating a first and a second mixed signal based on a mixture of the first reception radiation with a first local oscillator radiation or based on a mixture of the second reception radiation with a second local oscillator radiation, respectively, for a distance measurement according to the principle of a frequency-modulated continuous wave radar, and
• iv. a processing unit configured for determining at least one distance to the target based on the first and the second mixed signal,
• wherein the processing unit is configured to determine a parameter, which is indicative of a frequency offset between the first and the second modulation band, and to take the parameter into consideration during the determination of the at least one distance to the target to derive a frequency difference between the first frequency modulation and the second frequency modulation.