Abstract: A variable synthetic wavelength absolute distance measuring device locked to a dynamic sideband and a method thereof are disclosed. A high-frequency electro-optic phase modulator driven by an adjustable clock source to modulate a single-frequency reference laser to generate laser sidebands with equal frequency intervals. The tunable laser is locked to the fifth-order sideband through an offset frequency locking technology. After locking, the interval frequency of the sideband is determined by the adjustable clock source, namely dynamic sideband. The frequency of the adjustable clock source is dynamically adjusted, the interval frequency of the sideband and the frequency difference between the two lasers will change accordingly. Combined with the multi-wavelength interferometry, the constructed synthetic wavelength is also determined by the adjustable clock source, that is, the variable synthetic wavelength.

Abstract: A variable synthetic wavelength absolute distance measuring device locked to a dynamic sideband and a method thereof are disclosed. A high-frequency electro-optic phase modulator driven by an adjustable clock source to modulate a single-frequency reference laser to generate laser sidebands with equal frequency intervals. The tunable laser is locked to the fifth-order sideband through an offset frequency locking technology. After locking, the interval frequency of the sideband is determined by the adjustable clock source, namely dynamic sideband. The frequency of the adjustable clock source is dynamically adjusted, the interval frequency of the sideband and the frequency difference between the two lasers will change accordingly. Combined with the multi-wavelength interferometry, the constructed synthetic wavelength is also determined by the adjustable clock source, that is, the variable synthetic wavelength.

Abstract: The disclosure discloses a differential sinusoidal phase modulation laser interferometric nanometer displacement measuring apparatus and method. The beam output from the single-frequency laser is converted into a 45° linearly polarized beam after passing through the polarizer, then projected onto two sets of sinusoidal phase modulation interferometers consisting of the beam splitter, the electro-optic phase modulator, the half wave plate, three pyramid prisms, two polarization beam splitters, thereby forming measurement and reference interference signals which are received by two photodetectors. A high-frequency sinusoidal voltage signal is applied to the electro-optic phase modulator placed in the common reference arm of the two interferometers, thereby modulating the interference signal into a high-frequency AC signal. By detecting the difference between the phase change amounts of the two interference signals when the measured object moves, the measured displacement can be obtained.

Abstract: A reference laser beam locked to a femtosecond optical frequency comb is modulated through a high frequency electro-optic phase modulator, and laser sidebands with equal intervals are generated. Beat frequency is performed on the sixth-order sideband and the frequency sweeping laser beam, a beat signal and a frequency sweeping signal source are down-mixed to generate a difference frequency signal, and the difference frequency signal is locked to a reference clock through a digital phase detector and a PID controller. The frequency sweeping laser beam is locked to reference laser beam with a dynamic offset frequency under the closed loop control, and sinusoidal frequency sweeping is simultaneously performed together with the frequency sweeping signal source. The locked laser beam is used for absolute distance measurement, and a distance to be measured is obtained according to the synthetic wavelength transition theory.

Abstract: The disclosure discloses a phase delay extraction and compensation method in a PGC phase demodulation technology. The sinusoidal phase modulation interference signal is converted into a digital interference signal by an analog-to-digital converter after amplification and filtering, and the digital interference signal is subjected to orthogonal downmixing of first-order, second-order, and fourth-order harmonics simultaneously to obtain three pairs of orthogonal harmonic amplitude signals.

Abstract: The disclosure discloses a differential sinusoidal phase modulation laser interferometric nanometer displacement measuring apparatus and method. The beam output from the single-frequency laser is converted into a 45° linearly polarized beam after passing through the polarizer, then projected onto two sets of sinusoidal phase modulation interferometers consisting of the beam splitter, the electro-optic phase modulator, the half wave plate, three pyramid prisms, two polarization beam splitters, thereby forming measurement and reference interference signals which are received by two photodetectors. A high-frequency sinusoidal voltage signal is applied to the electro-optic phase modulator placed in the common reference arm of the two interferometers, thereby modulating the interference signal into a high-frequency AC signal. By detecting the difference between the phase change amounts of the two interference signals when the measured object moves, the measured displacement can be obtained.

Abstract: An identity verification method performed at a terminal includes playing in an audio form action guide information including mouth shape guide information selected from a preset action guide information library at a speed corresponding to the action guide information, and collecting a corresponding set of action images within a preset time window; performing matching detection on the collected set of action images and the action guide information, to obtain a living body detection result indicating whether a living body exists in the collected set of action images; according to the living body detection result that indicates that a living body exists in the collected set of action images: collecting user identity information and performing verification according to the collected user identity information, to obtain a user identity information verification result; and determining the identity verification result according to the user identity information verification result.

Abstract: A reference laser beam locked to a femtosecond optical frequency comb is modulated through a high frequency electro-optic phase modulator, and laser sidebands with equal intervals are generated. Beat frequency is performed on the sixth-order sideband and the frequency sweeping laser beam, a beat signal and a frequency sweeping signal source are down-mixed to generate a difference frequency signal, and the difference frequency signal is locked to a reference clock through a digital phase detector and a PID controller. The frequency sweeping laser beam is locked to reference laser beam with a dynamic offset frequency under the closed loop control, and sinusoidal frequency sweeping is simultaneously performed together with the frequency sweeping signal source.

Abstract: The disclosure discloses a phase delay extraction and compensation method in a PGC phase demodulation technology. The sinusoidal phase modulation interference signal is converted into a digital interference signal by an analog-to-digital converter after amplification and filtering, and the digital interference signal is subjected to orthogonal downmixing of first-order, second-order, and fourth-order harmonics simultaneously to obtain three pairs of orthogonal harmonic amplitude signals.

Abstract: An identity verification method performed at a terminal includes playing in an audio form action guide information including mouth shape guide information selected from a preset action guide information library at a speed corresponding to the action guide information, and collecting a corresponding set of action images within a preset time window; performing matching detection on the collected set of action images and the action guide information, to obtain a living body detection result indicating whether a living body exists in the collected set of action images; according to the living body detection result that indicates that a living body exists in the collected set of action images: collecting user identity information and performing verification according to the collected user identity information, to obtain a user identity information verification result; and determining the identity verification result according to the user identity information verification result.

Abstract: An identity verification method performed at a terminal includes: displaying and/or playing in an audio form action guide information selected from a preset action guide information library, and collecting a corresponding set of action images within a preset time window; performing matching detection on the collected set of action images and the action guide information, to obtain a living body detection result indicating whether a living body exists in the collected set of action images; according to the living body detection result that indicates that a living body exists in the collected set of action images: collecting user identity information and performing verification according to the collected user identity information, to obtain a user identity information verification result; and determining the identity verification result according to the user identity information verification result.

Abstract: An identity verification method performed at a terminal includes: displaying and/or playing in an audio form action guide information selected from a preset action guide information library, and collecting a corresponding set of action images within a preset time window; performing matching detection on the collected set of action images and the action guide information, to obtain a living body detection result indicating whether a living body exists in the collected set of action images; according to the living body detection result that indicates that a living body exists in the collected set of action images: collecting user identity information and performing verification according to the collected user identity information, to obtain a user identity information verification result; and determining the identity verification result according to the user identity information verification result.