Multi-axis Interference Signal Processing Method and System

Abstract

A multi-axis interferometric signal processing method and system are disclosed. The method includes the following steps: a second measurement beam and a third measurement beam are reflected by a first measurement mirror and a second measurement mirror arranged on different axes, respectively, and merged with the first measurement beam to form a beam with a beat frequency; the beat frequency beam is received and converted into a measurement signal; a reference signal and the measurement signal are received, and phase information is obtained through signal splitting technology and lock-in amplification technology; the displacement of the first measurement mirror and the second measurement mirror is calculated based on the phase information. This allows for the reception of measurement signals in two axes using a single photodetector, and the displacement in both axes can be calculated through back-end signal processing technology, thus significantly simplifying the number of optical components.

Claims

1. A multi-axis interference signal processing method, comprising the following steps: (A) generating a first beam, a second beam, and a third beam with a fixed frequency difference using a multi-frequency laser unit capable of producing laser light of multiple wavelengths; (B) splitting the first beam into a first reference beam and a first measurement beam, splitting the second beam into a second reference beam and a second measurement beam, and splitting the third beam into a third reference beam and a third measurement beam; (C) merging the first reference beam, the second reference beam, and the third reference beam and converting them into a reference signal; (D) reflecting the second measurement beam and the third measurement beam by a first measurement mirror and a second measurement mirror respectively arranged on different axes, and merging them with the first measurement beam to form a beam with a beat frequency, receiving the beam with the beat frequency, and converting it into a measurement signal; (E) Receive the reference signal and the measurement signal, and obtain the phase information of the beam with the beat frequency through signal splitting technology and phase-locked amplification technology; and (F) Calculate a first displacement of the first measurement mirror and a second displacement of the second measurement mirror based on the phase information.

2. The multi-axis interference signal processing method as described in claim 1, wherein, In step (E), the following sub-steps are also included: (E1) The reference signal is passed through a first bandpass filter and a second bandpass filter to obtain a first frequency difference reference signal with the frequency difference between the first beam and the second beam, and a second frequency difference reference signal with the frequency difference between the first beam and the third beam, respectively; the measurement signal is passed through a third bandpass filter and a fourth bandpass filter to obtain a first frequency difference measurement signal with the frequency difference between the first beam and the second beam, and a second frequency difference measurement signal with the frequency difference between the first beam and the third beam, respectively. (E2) Pass the first frequency difference reference signal and the first frequency difference measurement signal sequentially through a first multiplier and a first low-pass filter to obtain a first output signal; pass the second frequency difference reference signal and the second frequency difference measurement signal sequentially through a second multiplier and a second low-pass filter to obtain a second output signal; and (E3) Obtain the phase information corresponding to the first measurement mirror from the first output signal and calculate the first displacement of the first measurement mirror; obtain the phase information corresponding to the second measurement mirror from the second output signal and calculate the second displacement of the second measurement mirror.

3. The multi-axis interference signal processing method as described in claim 1, wherein, In steps (C) and (D), the DC signal in the reference signal and the measurement signal is filtered out.

4. The multi-axis interference signal processing method as described in claim 1, wherein, In step (A), the frequency difference between the first beam, the second beam, and the third beam is not an overtone relationship.

5. The multi-axis interference signal processing method as described in claim 1, wherein, Step (A) further includes the following sub-steps: (A1) causing a single-mode laser light source to emit the first beam having a first frequency; (A2) causing a portion of the first beam to be converted into the second beam having a second frequency via a first optical modulator; and (A3) causing another portion of the first beam to be converted into the third beam having a third frequency via a second optical modulator.

6. The multi-axis interference signal processing method as described in claim 1, wherein, Step (A) further includes the following sub-steps: (A4) causing a dual-mode laser light source to emit a first beam having a first frequency and a second beam having a second frequency; and (A5) causing a portion of the second beam to be converted into a third beam having a third frequency via a third optical modulator.

7. A multi-axis interferometric signal processing system, comprising: a multi-frequency laser unit for generating a first beam, a second beam, and a third beam having a fixed frequency difference; a beam splitting unit for splitting the first beam into a first reference beam and a first measurement beam, the second beam into a second reference beam and a second measurement beam, and the third beam into a third reference beam and a third measurement beam; a reference unit including a first photodetector for receiving the merged first reference beam, the second reference beam, and the third reference beam, and converting them into a reference signal; and a measurement unit including a positioning platform, a first measurement mirror and a second measurement mirror mounted on the positioning platform and disposed on different axes, and a second photodetector, wherein the second measurement beam and the third measurement beam are reflected by the first measurement mirror and the second measurement mirror, respectively, and merged with the first measurement beam to form a beam with a beat frequency, and the second photodetector receives the beam with the beat frequency and converts it into a measurement signal; A signal processing unit is used to receive the reference signal and the measurement signal and perform signal processing to obtain the phase information of the beam with the beat frequency, and to calculate a first displacement of the first measuring mirror and a second displacement of the second measuring mirror from the phase information through signal splitting technology and phase-locked amplification technology.

8. The multi-axis interference signal processing system as described in claim 7, wherein, The multi-frequency laser unit includes a single-mode laser light source, a first optical modulator, and a second optical modulator. A portion of the first light beam passes through the first optical modulator to form a second light beam with a second frequency, and another portion of the first light beam passes through the second optical modulator to form a third light beam with a third frequency.

9. The multi-axis interference signal processing system as described in claim 7, wherein, The multi-frequency laser unit includes a dual-mode laser light source and a third optical modulator. The dual-mode laser light source emits a first beam with a first frequency and a second beam with a second frequency. A portion of the second beam passes through the third optical modulator to form a third beam with a third frequency.

10. The multi-axis interference signal processing system as described in claim 7, wherein, The signal processing unit includes a first bandpass filter, a second bandpass filter, a third bandpass filter, and a fourth bandpass filter. The first bandpass filter allows the portion of the reference signal carrying the frequency difference signal between the first beam and the second beam to pass through, thus becoming a first frequency difference reference signal. The second bandpass filter allows the portion of the reference signal carrying the frequency difference between the first beam and the third beam to pass through, thus becoming a second frequency difference reference signal. The third bandpass filter allows the portion of the measurement signal carrying the frequency difference between the first beam and the second beam to pass through, thus becoming a first frequency difference measurement signal. The fourth bandpass filter allows the portion of the reference signal carrying the frequency difference between the first beam and the third beam to pass through, thus becoming a second frequency difference measurement signal.

11. The multi-axis interference signal processing system as described in claim 10, wherein, The signal processing unit further includes a first multiplier, a second multiplier, a first low-pass filter, and a second low-pass filter. The first multiplier and the first low-pass filter allow the first frequency difference reference signal and the first frequency difference measurement signal to pass through sequentially to obtain a first output signal. The second multiplier and the second low-pass filter allow the second frequency difference reference signal and the second frequency difference measurement signal to pass through sequentially to obtain a second output signal.

Images