182 results about "Lock-in amplifier" patented technology

The invention relates to the technical field of quantum sensing and ocean detection, and discloses an ocean magnetic field sensor based on an NV color center and an ocean magnetic field measuring method.The sensor comprises a cylindrical pressure-resistant cabin, an optical platform arranged in the pressure-resistant cabin and a main control panel; a laser, a beam shaping unit, a dichroscope, a beam shaping lens group, an objective lens, a diamond NV color center chip, a plano-convex lens I, a band-pass filter and a photoelectric detector are mounted on the optical platform; two microstrip loop antennas are mounted on the outer side of the diamond NV color center chip; an FPGA + ARM dual-core processor, a digital lock-in amplifier and two microwave signal generators are installed on the main control board, and the microwave signal generators are connected with the microstrip loop antenna and achieve electromagnetic coupling with the diamond NV color center chip. The invention has the advantages of high sensitivity, good long-term stability and strong anti-interference capability, and provides a new generation of quantum sensing solution for applications such as ocean geomagnetic monitoring and underwater target identification.

The invention discloses a nonlinear dielectric constant measuring system based on a scanning nonlinear dielectric microscope, comprising: a probe, one end of which forms a micro capacitance Cs with the upper surface of a sample to be tested; the low-frequency signal module applies a low-frequency signal to the lower surface of the to-be-tested sample; the other end of the probe is connected with an LC resonance circuit in the probe module; the output end of a signal amplifier in the probe module is connected with a frequency modulation demodulator; the frequency modulation demodulator demodulates the frequency signal modulated by the probe module, removes a high-frequency carrier signal, inputs the demodulated signal into the lock-in amplifier, and detects, separates and amplifies a high-signal-to-noise-ratio signal by taking the frequency of a low-frequency signal applied to the sample to be tested as a reference frequency; according to the measurement system, the detection speed, the service life of the probe and the multi-material applicability can be remarkably improved, meanwhile, the thermal disturbance effect is inhibited, and a reliable solution is provided for accurate characterization of nano electronic devices.

The invention relates to the technical field of quantum sensing, and discloses a quantum magnetometer device based on diamond NV color center photoelectric detection magnetic resonance. Wherein the optical path module performs optical excitation and imaging positioning on a diamond sample through a laser and an objective lens. The circuit module integrates a microwave source, a lock-in amplifier, a low-noise current amplifier and a programmable power supply, applies a microwave field and bias voltage to a microwave antenna and an interdigital electrode on the surface of a sample respectively, and collects sample dependency photocurrent signals. And the operation module realizes automatic control and data processing of the system. According to the device, NV color center spin state information is converted into a photocurrent signal through a photoelectric detection magnetic resonance mechanism, an amplitude or frequency modulated signal is demodulated by using a lock-in amplification technology, information of a detection magnetic field is obtained through a high signal-to-noise ratio photoelectric detection magnetic resonance spectrum, and the sensitivity of the magnetic field is evaluated. Magnetic resonance signals are detected in an all-electricity mode, a complex optical system of traditional fluorescence detection is simplified, and the device has the advantages of being compact in structure, easy to integrate, high in measurement sensitivity and the like.

The invention relates to the field of mining laser gas detection, in particular to a modulation and demodulation method and system for carrier noise suppression, and the modulation and demodulation method comprises the following steps: S1, generating a driving current sequence through a laser gas sensor; s2, collecting a light intensity sequence to carry out data reconstruction; s3, extracting a harmonic signal, sending the reconstructed sequence into a lock-in amplifier, and respectively extracting a second harmonic signal and a first harmonic signal; and S4, detecting the gas concentration through the ratio by using the mapping relation between the gas concentration and the ratio of the second harmonic signal to the first harmonic signal. According to the method, a continuous data discrete reconstruction technology is introduced into a modulation and demodulation process, and a reference time sequence is generated by utilizing the characteristics of a laser output signal, so that self-matching and dynamic adjustment of modulation frequency are realized, external signal interference is effectively avoided, and the harmonic extraction stability is improved; meanwhile, the hardware structure is simplified, and the adaptability of the system to different gas absorption spectral lines is enhanced.

The invention discloses a device and a method for measuring the velocity field of an autoclave through hot-pressing wind speed. The device comprises a thermosensitive probe, a Wheatstone bridge, a lock-in amplifier, an NI multi-channel data acquisition card and a computer, the thermosensitive probe is used for instantaneously detecting the temperature of a placement point position and generating resistance fluctuation based on sensing temperature change; the Wheatstone bridge is formed by connecting a fixed resistor, a variable resistor and a thermosensitive probe, and is used for forming a series circuit with the lock-in amplifier; the lock-in amplifier is used for supplying power to the Wheatstone bridge and providing co-frequency voltage at the same time, so that resistance data of a thermosensitive probe in the Wheatstone bridge is converted into voltage data to be output; the NI multi-channel data acquisition card is used for acquiring in-phase component voltage signals output by the lock-in amplifier; the computer is used for processing the voltage data to obtain the average speed and the pulsation speed of the measurement point. According to the invention, the problems of limited precision, insufficient sensitivity and poor adaptability to the internal environment of the autoclave in the conventional gas speed measurement method are solved.

The invention relates to a high-precision temperature detection system based on an alternating-current impedance bridge. The high-precision temperature detection system comprises a double-resistance bridge circuit, a lock-in amplifier and a differential circuit, the double-resistor bridge circuit comprises a resistive temperature sensor and a standard resistor which are connected in series, and the phase-locked amplifier is a digital phase-locked amplifier realized based on an FPGA (Field Programmable Gate Array). Wherein the initial potential of a first voltage measurement end arranged at the midpoint of the double-resistor bridge circuit is zero by adjusting the two excitation signals which are loaded to the double-resistor bridge circuit and have the same frequency and opposite phases before temperature measurement; in the temperature measuring process, the lock-in amplifier detects the potential of the first voltage measuring end and the voltage at the two ends of the standard resistor through the differential circuit, then the resistance value of the resistance-type temperature sensor is calculated by combining the resistance value of the standard resistor, and then the temperature of the resistance-type temperature sensor is reduced. According to the invention, the anti-interference capability can be improved, and the measurement precision of 0.1 mK level can be reached near 273K.

A measurement system includes: a first laser device for outputting a pump light as a pulse laser in response to an input first signal; a second laser device for outputting a probe light as a pulse laser in response to an input second signal; a trigger generator and delay time controller for inputting the first signal and the second signal to the first laser and the second laser, repeatedly inputting the first signal and the second signal by switching a variable delay value which is a difference between a timing of inputting the first signal to the first laser and a timing of inputting the second signal to the second laser in a plurality of ways, and outputting a reference signal to a lock-in amplifier when switching the variable delay value; an auxiliary optical system for guiding the pump light and the probe light to sample; a cantilever having an probe tip disposed proximate to the sample; and a controller for applying a periodically varying voltage to the cantilever and outputting a change amount signal which is a voltage or a current corresponding to a change in the resonance frequency of the cantilever, wherein the lock-in amplifier measures the change amount signal based on reference signal.

The invention discloses a rheology-birefringence combined in-situ testing device and method based on chopper rotation frequency signals, belongs to the technical field of optical testing, and aims to solve the technical problems that an existing Spark-FB device is low in measurement accuracy and limits application scenes. The laser emitter emits a light beam along a set angle (forming an angle of 45 degrees with the horizontal plane), the light beam is converted into linearly polarized light through the polarizer, and an optical signal is modulated through the rotating chopper; the modulated light beam penetrates through a polymer sample to which a shear flow field is applied by a commercial rheometer, and transmission light carrying optical anisotropy information of the sample sequentially passes through a 1 / 4 wave plate and a polarization analyzer, and is finally received by a photoelectric detector and transmitted to a lock-in amplifier for analysis. According to the invention, an independent datum reference signal is provided through the chopper, decoupling and combination of a commercial rheometer and a birefringence light path are realized, and synchronous and accurate in-situ measurement of rheological and optical properties of a high polymer material under a deformation condition can be realized.

The invention relates to a Rydberg atomic communication receiving system and method based on AT split peak value analysis, and belongs to the technical field of quantum communication. The system comprises a detection laser, a coupling laser, an AOM / EOM, a function generator, a high-frequency signal generator, a cesium atom gas chamber, a photoelectric detector, a lock-in amplifier, a data acquisition module and a microwave signal output module. The AOM / EOM modulates the frequency of the detection laser; the microwave signal output module generates an AM modulation microwave signal and transmits the AM modulation microwave signal to the cesium atom gas chamber, so that the target Rydberg state atoms generate an AT splitting effect to calibrate system parameters; the photoelectric detector and the lock-in amplifier obtain a first harmonic component based on the transmission light. During communication, the system is arranged in a microwave electric field received by communication, and the data acquisition and processing module outputs AM modulation microwave signals received by the recovered cesium atom gas chamber based on calibrated system parameters and phase locking. The method solves the problem of signal distortion existing in EIT-AT direct communication transmission and the problem of tedious operation of a heterodyne method.

The invention relates to a resonant optical gyroscope signal detection method based on an optical switch. The resonant optical gyroscope signal detection method comprises the following steps: step 1, adopting a narrow linewidth laser as a light source; 2, the split light field enters a lithium niobate phase modulator A and a phase modulator B to be modulated by a triangular wave voltage signal, the light field subjected to phase modulation is coupled in opposite directions to enter a waveguide resonant cavity, and a photoelectric detector A and a photoelectric detector B are used at the output end of the resonant cavity to obtain a voltage signal; and voltage signals obtained by the photoelectric detector A and the photoelectric detector B are accessed to a lock-in amplifier. 3, arranging an optical switch A between the waveguide resonant cavity and the photoelectric detector A; and an optical switch b is arranged between the waveguide resonant cavity and the photoelectric detector B, so that the detection of a gyro signal is completed. The interference of polarization noise can be reduced, and the resonant frequency locking precision and the angular velocity detection sensitivity of the gyroscope are improved.

According to various embodiments, a sensing device for measuring oxygen concentration cycles in breath is disclosed. The sensing device includes a laser configured to emit light at an A-band of oxygen, a lens configured to collimate the light, and a multi-pass cell configured to contain a replaceable sample cell. The light passes through the multi-pass cell and is attenuated by oxygen in the sample cell. The sensing device further includes a photodetector configurated to convert the attenuated light into an electrical signal, and a lock-in amplifier or an equivalent processing circuit configured to determine oxygen concentration from the electrical signal.

The invention discloses an all-optical-fiber liquid level measuring system and method based on double-optical-comb phase decoupling and self-adaptive compensation, and the system comprises a double-optical-comb light source module, an optical fiber coupling module, a signal collection and processing system, a self-adaptive compensation module, a measuring arm and a reference arm. The optical fiber coupling module comprises a polarization-maintaining optical fiber beam splitter and a polarization-maintaining optical fiber beam combiner; the signal acquisition and processing system comprises a balance detector, a lock-in amplifier and an upper computer which are sequentially connected from front to back, and the lock-in amplifier is connected with a self-adaptive compensation module; the double-optical-comb light source module is connected with the measuring arm and the reference arm through the polarization-maintaining optical fiber beam splitter, and the measuring arm and the reference arm are connected with the balance detector through the polarization-maintaining optical fiber beam combiner. According to the invention, interference signal intensity and phase information are combined, the problem of reflectivity difference between transparent liquid and opaque liquid is solved, phase noise caused by environmental disturbance is eliminated, and the measurement stability is improved. According to the invention, non-contact, real-time and high-resolution measurement of the height of the liquid level is realized, especially measurement in a high-pressure, high-temperature or corrosive environment is realized, and the application range is expanded.

The invention discloses a multi-mode nanometer measurement system and method based on terahertz scattering type scanning near-field optical microscopy and multi-frequency electrostatic force microscopy, and belongs to the technical field of near-field imaging, the measurement system comprises an AFM main body, a terahertz source, an optical path system, a terahertz detector, a multi-frequency signal generator and two phase-locked amplifiers; terahertz waves emitted by the terahertz source reach the terahertz detector through the optical path system, and near-field optical signals are obtained. The AFM comprises a metal coating probe; the multi-frequency signal generator generates sinusoidal signals with frequencies of omega1 and omega2; a sample is placed on the scanner, and the cantilever beam is controlled to vibrate at the frequency omega 1; an alternating voltage with the frequency of omega 2 is applied to a metal coating probe arranged at the top end of the cantilever beam; laser emitted by the laser is reflected to the light spot position detector through the cantilever beam, and morphology and electrostatic force signals are obtained through the two lock-in amplifiers respectively. According to the invention, a morphology signal, an optical signal and an electrostatic force signal can be synchronously obtained through single scanning.

The present disclosure relates to a method and device for removing background noise in microscopic imaging based on frequency-domain modulation. The method includes irradiating a surface of a sample to be measured by simultaneously irradiating the surface of the sample by utilizing two beams from two laser devices. One of the two beams passes through a 0˜2π vortex phase plate and then focuses on the sample to be measured to form a high-energy hollow spot, and the other of the two beams focuses on the sample to be measured to form a low-energy solid spot. The method further includes modulating the two beams in time-domain simultaneously using an electro-optic modulator and demodulating signal light at different frequencies using a lock-in amplifier, then removing the background noise by a differential process to realize a high signal-to-noise ratio super-resolution image.

A system for automatically locking a control laser in a Rydberg atomic sensor may comprise an atomic vapor cell, a probe laser configured to excite the atoms in the atomic vapor cell to an intermediate energy state, and a control laser configured to excite the one or more atoms in the atomic vapor cell from the intermediate energy state to a higher energy state. The light generated by the control laser may be dithered at a pre-determined frequency. The system further comprises a photodiode configured to convert light received from the vapor cell into an electrical signal, a lock-in amplifier configured to generate an error signal based on the electrical signal received from the photo diode and a received reference oscillation frequency, and a servo configured to receive the generated error signal from the lock-in amplifier and adjust a frequency of the control laser based on the received error signal.

The invention relates to the technical field of thermal interface material defect detection, in particular to a nondestructive detection method and system for thermal interface material application defects, and the system comprises an electric displacement table, heating laser, detection laser, a photoelectric detector, an acoustic optical modulator, a lock-in amplifier, an optical element and a data processing unit; the electric displacement table is used for fixing a sample and accurately controlling the position of the sample; the sample is of a silicon-thermal interface material-substrate sandwich structure; the upper-layer silicon wafer of the sample is plated with a metal film as a transduction layer; the heating laser is used for heating the sample; the acoustic optical modulator is used for modulating the heating laser, so that the heating laser heats the sample in a sine wave form; the detection laser is used for detecting sample temperature fluctuation; the photoelectric detector is used for collecting and detecting laser reflection signals; the lock-in amplifier is used for extracting and detecting laser phase and amplitude signals. According to the invention, non-destructive rapid detection of the defects of the thermal interface material in an application scene can be realized.

The invention relates to the technical field of quantum precision measurement and automatic control, and discloses a Rydberg atom AT split signal-based closed-loop locking detection method and a Rydberg atom AT split signal-based closed-loop locking detection system. The method comprises the following steps: acquiring an EIT signal under the condition of no microwave field, and locking the frequency of coupled laser at a preset reference point to establish a frequency reference; the coupled laser and the detection laser are combined and then collinearly penetrate through the gas chamber; when the to-be-measured microwave field is applied to the gas chamber to generate AT splitting, the laser frequency shifter controls the frequency of the coupled laser to be switched between preset target frequency points; a lock-in amplifier is used for carrying out phase-sensitive detection on a detection laser light path transmission intensity signal, an error voltage signal is generated based on an AT split signal, and error voltage zero crossing points corresponding to two AT split peaks are locked through a servo controller; and calculating the to-be-measured microwave electric field intensity according to the locking point feedback control quantity difference. According to the invention, the measurement precision is improved, the anti-interference capability is enhanced, the working stability is improved, and rapid and stable detection of the microwave electric field is realized.

The present invention relates to an optical modulation system based on the interaction of two collinear light beams having different wavelengths passing through a cuvette containing a solution of Cs2SnI6, comprising a pumping laser emitter emitting a modulated pumping beam with a wavelength between 355 nm and 1550 nm and with a variable frequency; a test laser emitter emitting a continuous wave test beam at 633 nm and with a power limited to 10 mW; a beam splitter where the pumping and test beams are combined to strike on the cuvette; a pass filter that removes the signal from the pumping beam; a spatial analysis camera; a time / frequency analysis equipment with a photodetector, a commercial lock-in amplifier and an oscilloscope; and a signal generator.

The application provides a precision large-bandwidth digital phase-locked amplifier with a hybrid sampling structure, comprising a signal-to-be-tested link, a reference signal link, a digital logic and a computing system; the signal-to-be-tested link inputs a signal to be tested, and outputs a first analog-to-digital conversion signal and a second analog-to-digital conversion signal to the digital logic and the computing system; the reference signal link inputs a reference signal, and outputs a third analog-to-digital conversion signal and a hysteresis comparison signal to the digital logic and the computing system; the digital logic and the computing system output a plurality of control signals to the signal-to-be-tested link and the reference signal link; the digital phase-locked amplifier with the hybrid sampling structure has a low-frequency sampling mode, a frequency down-conversion sampling mode and a high-frequency sampling mode, and the signal-to-be-tested link can improve the signal-to-noise ratio in the measurement of low-frequency signals and high-frequency signals.

The application relates to the technical field of laser heterodyne atmospheric remote sensing, and discloses a laser heterodyne atmospheric remote sensing device and method applied to a ship, the device comprising a sun tracking module, a heterodyne light path module, a signal processing module and a computer device, wherein the sun tracking module comprises a sun tracking meter, a photoelectric detector and an optical switch, the heterodyne light path module comprises a laser, an optical attenuator, an optical fiber combiner and a photoelectric detector; the signal processing module comprises a radio frequency amplifier, a radio frequency filter, a power detector, a lock-in amplifier and a data collector. The laser heterodyne atmospheric remote sensing device applied to the ship can reduce the precision requirement of a sun tracking meter for laser heterodyne detection, and realizes spectral detection under the condition that the probability of the alignment precision being within the range of 0.1 degrees is greater than 50%.

This invention proposes a dual-resonance coherent population trapping magnetometer and its implementation method, which can effectively suppress optical noise of lasers, improve sensitivity, and increase the lower limit of the measurement range. It includes: a first microwave source, a second microwave source, a first current source, a second current source, a first bias-T, a second bias-T, a first VCSEL laser, a second VCSEL laser, a first collimating lens, a second collimating lens, a first PBS, and a λ / 2 waveplate. 87 The system includes an Rb atom gas cell, a second PBS, a first photodiode, a second photodiode, a differential amplifier, and a dual-channel lock-in amplifier. The first VCSEL laser, the second VCSEL laser, the first collimating lens, the second collimating lens, the first PBS, and the λ / 2 waveplate are located at... 87 On the left side of the Rb atomic gas cell, the first VCSEL laser and the first collimating lens are located to the left of the first PBS, and the second VCSEL laser and the second collimating lens are located below the first PBS. The laser output from the second VCSEL laser is reflected by the first PBS and propagates towards the right atomic gas cell.

The utility model discloses a quartz enhanced photoacoustic spectrometry gas detection system based on coaxial main and auxiliary resonance tubes, which comprises a signal generator, an adder, a laser, a collimator, a gas sensing device, a preamplifier, a lock-in amplifier, a data acquisition system and a computer, a laser is arranged on one side of the summator, a collimator is arranged at the output end of the laser, a gas sensing device is arranged on one side of the collimator, a pre-amplifier is arranged on the rear side of the gas sensing device, and the output end of the pre-amplifier is connected with the input end of the phase-locked amplifier. The output end of the lock-in amplifier is connected with the data acquisition system, and the data acquisition system is connected with the computer. The ultra-low trace gas detection device is used for ultra-low trace gas detection, gas concentration detection is rapid, accurate and effective, and the minimum detection limit of gas can be obviously enhanced.

The enrichment-enhanced photoacoustic spectrometry gas detection device comprises a signal generator, the signal output end of the signal generator is connected with the signal input end of a tunable laser light source, and the signal output end of the signal generator is connected with the signal input end of a lock-in amplifier; a light source emitted by the tunable laser light source penetrates through first glass of the photoacoustic cell to enter the photoacoustic cell, the gas inlet end and the gas outlet end of the photoacoustic cell are communicated with the enrichment enhancement gas circuit, and the signal output end of a microphone of the photoacoustic cell is connected with the signal input end of the lock-in amplifier. The signal output end of the lock-in amplifier is connected with the signal input end of the processor; through the signal enhancement module formed by the enrichment enhancement gas circuit and the photoacoustic cell, the local concentration of the sample gas entering the photoacoustic cell is increased, and the absorption of the detected gas to the laser is enhanced, so that the detection sensitivity is improved, the response time is shorter, the dynamic range is wider, and the concentration calibration linearity of gas sensing is better.

The application belongs to the technical field of photo-thermal spectrum gas detection, and particularly relates to a photo-thermal spectrum gas detection device and method based on a tapered optical fiber, which comprises an optical fiber gas chamber, a pump laser, a first wavelength division multiplexer, a second wavelength division multiplexer, a circulator, a probe laser, a photoelectric detector, a low-pass filter, a PID feedback control module, a power divider, a processor and a lock-in amplifier. Compared with the existing photo-thermal spectrum gas detection method and device based on a hollow optical fiber, the application can accelerate the gas sensing reaction speed, and on the other hand, due to the fact that the thermal-optic effect and the thermal expansion coefficient of the optical fiber material are significantly greater than those of the gas, the photo-thermal spectrum signal intensity of the tapered optical fiber will be significantly greater than that of the hollow optical fiber.

The application provides a Fe3O4 nanoparticle microscopic imaging detection method based on left and right polarization modulation, belongs to the technical field of photothermal science and detection and signal processing, and solves the problems that current nanometer single particles are difficult to observe and physical and chemical characteristics are difficult to obtain, and specifically comprises the following steps: determining a sample to be detected and preparing a slide sample; starting a computer, a data acquisition card, a lock-in amplifier, a galvanometer controller and a function generator; starting a power supply of an excitation light and a detection light laser and a refrigerator; setting detection parameters, setting laser power / current parameters, setting modulation parameters, and scanning and detecting the sample to be detected; loading a magnetic field; reading signals from the data acquisition card by the computer to obtain a photothermal detection result image; changing different laser parameters and the size of the magnetic field, repeating the above steps, obtaining a circular dichroism and magnetic circular dichroism detection result, measuring a magnetization curve, and monitoring a single nanoparticle magnetic moment flipping process.

The application discloses a kind of gas chamber polarization enhancement magnetometer based on multifocal holographic super surface and measuring method, belong to magnetic field measurement technical field.The magnetometer includes laser generation and control module, 1 / 4 wave plate, multifocal holographic super surface, optical magnetic resonance module, optical pumping signal post-processing module and reflector.Laser is collimated after 1 / 4 wave plate and is incident to multifocal holographic super surface, the super surface carries out phase control to incident light, makes multiple focal planes in different depths in gas chamber, improves the spatial uniformity of light pumping, enhances alkali atom polarization rate.Transmitted light enters optical pumping signal post-processing module, passes through polarizing beam splitter prism polarizing beam splitter prism, balanced differential detector and lock-in amplifier, extracts magnetic resonance signal and calculates magnetic field intensity.The application optimizes light pumping process, improves the stability and signal-to-noise ratio of magnetic measurement system, reduces measurement error, and is suitable for geomagnetic detection, biological magnetic signal detection and other high-sensitivity magnetic field measurement fields.

The application relates to the technical field of magnetic variable measurement, in particular to a magnetic induction electric field dynamic compensation control method based on online disturbance response, which comprises the following steps: injecting a characteristic test signal to the induction axis of a magnetism sensor, extracting an amplitude-phase deflection response characteristic by using a digital lock-in amplifier to construct a dynamic mapping matrix, and online identifying the gain, time constant and pure lag measurement model parameters of a calibration coil loop; an error processing unit sets an error offset coefficient and generates a reverse compensation control instruction to drive a loop to generate an offset magnetic field; the intensity of a multi-node parasitic induction electric field is obtained as a dynamic weight, a Steiner-Weber algorithm is used to solve a space equivalent interference radiation center, and the test duty ratio and calibration weight of each node are adjusted. The application actively injects orthogonal signals to online decouple a measurement baseline drift, and adaptively cooperates with a multi-node measurement array, so that wide-band and extremely low dynamic residual measurement of a large-space alternating magnetic field is realized.

Embodiments of the present disclosure relate to inertial measurement circuits, corresponding apparatuses, and methods. In one embodiment, a circuit comprises: an inertial measurement unit configured to oscillate via a drive signal provided by a drive circuit apparatus; a lock-in amplifier configured to receive a sense signal from the inertial measurement unit and a reference demodulation signal as a function of the drive signal, and to provide an inertial measurement signal based on the sense signal, wherein the reference demodulation signal is affected by a variable phase error; a phase meter circuit apparatus configured to receive the drive signal and the sense signal, and to provide as a function of a phase difference between the drive signal and the sense signal; a phase correction signal for the reference demodulation signal and a correction node configured to apply the phase correction signal to the reference demodulation signal, such that in response to applying the phase correction signal to the reference demodulation signal, the phase error is maintained near a reference value.

Systems and methods of microscopy include and / or apply a laser light source configured to produce an excitation light; a modulator configured to modulate the excitation light to produce a modulated light; a pulse compressor configured to compress a pulse of the modulated light to produce a pre-compensated light; a beam scanner configured to raster scan the pre-compensated light on a sample; a detector configured to receive a light signal from the sample and produce a detection signal; and a lock-in amplifier configured to receive the detection signal and perform an electronic heterodyne amplification of the detection signal.

A leakage detection device for detecting leakage of compressed gas includes a microphone that collects an ultrasonic signal which is converted into an electrical signal and outputted. Lock-in amplifiers extract one of the electrical signals having a specific frequency corresponding to a leakage and a calculation circuit calculates a physical amount corresponding to an amplitude value of the signal having the specific frequency. A notification device provides a notification to a user depending on the physical amount calculated by the calculation circuit.