Ranging method and ranging system of femtosecond laser frequency comb synthesis wave interference

Abstract

The invention relates to a ranging method and a ranging system of femtosecond laser frequency comb synthesis wave interference. The ranging method and the ranging system of the femtosecond laser frequency comb synthesis wave interference comprises a femtosecond laser frequency comb, a Michelson interference system and the like. The light emitted by the femtosecond laser frequency comb enters a first spectroscope, transmission light through the first spectroscope is emitted to a first reflecting mirror, and reflected light returns to the first spectroscope through the first reflecting mirror. The emitted light is emitted to a second spectroscope through the first spectroscope, reflected light through the second spectroscope is emitted to a second reflecting mirror through a first single wavelength generating and frequency shifting light path, and the reflected light through the second reflecting mirror and the first single wavelength generating and frequency shifting light path returns to the second spectroscope. The emitted light through the second reflecting mirror is emitted to a third reflecting mirror through a second single wavelength generating and frequency shifting light path, and reflected light through the third reflecting mirror returns to the second spectroscope through the second single wavelength generating and frequency shifting light path. The reflected light through the second reflecting mirror and the reflected light through the third reflecting mirror are combined on the position of the second spectroscope, and are combined with light pulses of a gage beam, the interference signals of two wavelengths are divided through a diffraction grating and are respectively detected and received by two photoelectric detectors, and range measurement is completed.

Description

technical field [0001] The invention relates to a distance measurement method and a distance measurement system, in particular to a femtosecond laser frequency comb synthetic wave interference distance measurement method and a distance measurement system suitable for absolute distance measurement. Background technique [0002] Femtosecond laser frequency comb refers to the femtosecond pulse laser repetition rate (f rep , referred to as repetition frequency) and phase shift frequency (f ceo ) locked with the frequency reference source. The laser emitted by the femtosecond laser frequency comb is composed of a series of equally spaced ultrashort laser pulses (the pulse width is several femtoseconds) in the time domain, and there are a series of equally spaced discrete spectral lines in the corresponding frequency domain (the spectral lines look like Like a comb, hence the name frequency comb), the frequency separation of adjacent spectral lines is equal to the repetition fre...

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Problems solved by technology

Through the above analysis, it can be seen that the key factor affecting the ranging accuracy of this method is the alignment error of the two pulses, and the method of determining whether the pulses are aligned by judging the peak value of the signal (the present invention is called "extreme value method") The accuracy is relatively limited, which affects the measurement accuracy

[0004] At present, the method with the highest distance measurement accuracy is the single-wavelength laser heterodyne interferometry, but this method must solve the problem of determining the order of the interference fringe change (commonly known as the "large number" of the interference phase) when measuring the absolute distance. To determine this large number, the coarse-side accuracy of the distance needs to be better than a quarter of a single wavelength. Since the extreme value method in the above-mentioned femtosecond laser frequency comb ranging cannot achieve an accuracy better than a quarter of a single wavelength, Therefore, it is impossible to directly use single-wavelength laser heterodyne interference to improve the ranging accuracy of the extremum method.

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