Abstract: A method of tracking a face includes determining a current frame from video stream data in response to receiving a face tracking instruction; detecting a position of a face in the current frame, and obtaining a historical motion trajectory of the face in the current frame; predicting the position of the face in the current frame based on the historical motion trajectory to obtain a predicted position of the face; obtaining a correlation matrix of the historical motion trajectory and the face in the current frame based on the predicted position and the detected position; and updating the historical motion trajectory based on the correlation matrix, and tracking the face in a next frame based on the updated historical motion trajectory.

Abstract: A mode-locked fiber laser device is provided in the disclosure. The mode-locked fiber laser device includes a non-linear loop mirror, an optical splitter and a uni-directional loop. The uni-directional loop includes a polarization beam splitter and a Faraday rotator. The uni-directional loop is coupled to the non-linear loop mirror by the optical splitter to form a figure-8 optical path. A first output laser pulse output by the optical splitter is propagated to the polarization beam splitter. After being rotated 45 degrees by a Faraday rotator, the first output laser pulse is propagated back to the non-linear loop mirror to form a laser resonator. A second output laser pulse output by the optical splitter is propagated to the Faraday rotator to rotate the second output laser pulse 45 degrees, and the polarization beam splitter reflects the second output laser pulse to the outside of the mode-locked fiber laser device.

Abstract: A laser device with a ring laser resonator includes a polarization maintaining (PM) fiber, a first quarter waveplate, and an optical isolator. The PM fiber has a light input end and a light output end and is configured to guide a first linearly polarized light with a first phase along a fast axis of the PM fiber from the light input end and a second linearly polarized light with a second phase along a slow axis of the PM fiber from the input end. The first quarter waveplate is disposed at the light output end of the PM fiber and configured to convert the first and the second linearly polarized lights into left-handed and right-handed (or right-handed and left-handed) circularly polarized lights, respectively. The optical isolator is configured to unidirectionally transmit a laser pulse in the ring laser resonator.

Abstract: A ranging light source includes a light source, a frequency division device and a transmitter. The light source is configured to generate a comb laser. The frequency division device is configured to generate a plurality of emitting n laser beams. These emitting laser beams have different center frequencies respectively. The transmitter is configured to output the emitting laser beams. The light source, the frequency division device and the transmitter are located on a first optical path. On the optical path, the frequency division device is between the light source and the transmitter.

Abstract: A mode-locked fiber laser device is provided in the disclosure. The mode-locked fiber laser device includes a non-linear loop mirror, an optical splitter and a uni-directional loop. The uni-directional loop includes a polarization beam splitter and a Faraday rotator. The uni-directional loop is coupled to the non-linear loop mirror by the optical splitter to form a figure-8 optical path. A first output laser pulse output by the optical splitter is propagated to the polarization beam splitter. After being rotated 45 degrees by a Faraday rotator, the first output laser pulse is propagated back to the non-linear loop mirror to form a laser resonator. A second output laser pulse output by the optical splitter is propagated to the Faraday rotator to rotate the second output laser pulse 45 degrees, and the polarization beam splitter reflects the second output laser pulse to the outside of the mode-locked fiber laser device.

Abstract: A laser device with a ring laser resonator includes a polarization maintaining (PM) fiber, a first quarter waveplate, and an optical isolator. The PM fiber has a light input end and a light output end and is configured to guide a first linearly polarized light with a first phase along a fast axis of the PM fiber from the light input end and a second linearly polarized light with a second phase along a slow axis of the PM fiber from the input end. The first quarter waveplate is disposed at the light output end of the PM fiber and configured to convert the first and the second linearly polarized lights into left-handed and right-handed (or right-handed and left-handed) circularly polarized lights, respectively. The optical isolator is configured to unidirectionally transmit a laser pulse in the ring laser resonator.

Abstract: A method and an apparatus for optical frequency measurement, using one or two frequency-stabilized mode-locked laser combs operating at different repetition rates to mix with a laser under measurement (LUM) respectively so as to generate two beat frequencies. The ordinal comb number where the beat frequency is generated is determined by measuring the ordinal comb number difference where the two beat frequencies are generated at different repetition rates so as to obtain the frequency of the LUM. The ordinal comb number difference is measured by using a dispersion device to offer an approximate ordinal comb number or by operating a mode-locked laser at three different repetition rates.

Abstract: A method of absolute optical frequency measurement is realized by using mode-locked laser frequency combs to measure the optical frequency of an unknown laser. By varying the repetition frequency, the relative frequency location of the unknown laser to the beating comb line is determined according to the corresponding variation of the beat frequency. Also, by varying the offset frequency of the mode-locked laser, the real offset frequency detected by a self-referencing technique can be determined according to the corresponding variation of the beat frequency between the unknown laser and the mode-locked laser frequency combs. The mode number of the frequency comb is uniquely and adequately determined through measuring the beat frequencies between the unknown laser and the mode-locked laser frequency combs at various repetition frequencies and through measuring the corresponding mode number change, and hence the optical frequency of the unknown laser is determined.

Abstract: A method and an apparatus for optical frequency measurement, using one or two frequency-stabilized mode-locked laser combs operating at different repetition rates to mix with a laser under measurement (LUM) respectively so as to generate two beat frequencies. The ordinal comb number where the beat frequency is generated is determined by measuring the ordinal comb number difference where the two beat frequencies are generated at different repetition rates so as to obtain the frequency of the LUM. The ordinal comb number difference is measured by using a dispersion device to offer an approximate ordinal comb number or by operating a mode-locked laser at three different repetition rates.

Abstract: A method of absolute optical frequency measurement is realized by using mode-locked laser frequency combs to measure the optical frequency of an unknown laser. By varying the repetition frequency, the relative frequency location of the unknown laser to the beating comb line is determined according to the corresponding variation of the beat frequency. Also, by varying the offset frequency of the mode-locked laser, the real offset frequency detected by a self-referencing technique can be determined according to the corresponding variation of the beat frequency between the unknown laser and the mode-locked laser frequency combs. The mode number of the frequency comb is uniquely and adequately determined through measuring the beat frequencies between the unknown laser and the mode-locked laser frequency combs at various repetition frequencies and through measuring the corresponding mode number change, and hence the optical frequency of the unknown laser is determined.

Abstract: A mode locking device of fiber laser includes a bar structural body, having a central hollow region, extending along a reference line of the bar structural body. The central hollow region has two ends coupled with two collimators on a fiber laser loop. A polarization dependent isolator is disposed within the central hollow region of the bar structural body such that the laser ca propagate only in one direction. Several rotors are disposed within the central hollow region of the bar structural body. Each rotor has a protruding piece, for rotating the rotor along the reference line. The laser beam travels along the reference line and passes through the rotors. Several retardation waveplates are disposed on the rotator structures and can be rotated together with the rotors. Each waveplate is adjusted to an angle, such that the laser can be mode-locked automatically.

Abstract: A mode locking device of fiber laser includes a bar structural body, having a central hollow region, extending along a reference line of the bar structural body. The central hollow region has two ends coupled with two collimators on a fiber laser loop. A polarization dependent isolator is disposed within the central hollow region of the bar structural body such that the laser ca propagate only in one direction. Several rotors are disposed within the central hollow region of the bar structural body. Each rotor has a protruding piece, for rotating the rotor along the reference line. The laser beam travels along the reference line and passes through the rotors. Several retardation waveplates are disposed on the rotator structures and can be rotated together with the rotors. Each waveplate is adjusted to an angle, such that the laser can be mode-locked automatically.

Abstract: The present invention discloses a novel apparatus and method for stabilizing the frequency of a laser. To avoid the effect that a single-frequency absorption spectrum is easy to be affected by variations of laser power and the complexity to modulate a laser frequency, the present invention adopts at least two laser beams at different frequencies and obtains an error signal that is a difference in absorption spectrums of the laser beams. Since the error signal is a difference between two laser beams coming from an identical laser source, the variation of laser power could be eliminated. Furthermore, since the absorption spectrum is usually above hundreds of (MHz), the range of locked frequency of the present invention is large, and the laser frequency is not easily unlocked due to outside disturbance.

Abstract: The present invention discloses a novel apparatus and method for stabilizing the frequency of a laser. To avoid the effect that a single-frequency absorption spectrum is easy to be affected by variations of laser power and the complexity to modulate a laser frequency, the present invention adopts at least two laser beams at different frequencies and obtains an error signal that is a difference in absorption spectrums of the laser beams. Since the error signal is a difference between two laser beams coming from an identical laser source, the variation of laser power could be eliminated. Furthermore, since the absorption spectrum is usually above hundreds of (MHz), the range of locked frequency of the present invention is large, and the laser frequency is not easily unlocked due to outside disturbance.