347 results about "Wavelength modulation" patented technology

The invention discloses an optical fiber distributed multi-point methane real-time monitor based on the light wave modulation spectrometry and the monitoring method, a semiconductor DFB laser, an optical fiber splitter, a gas calibration pond, a laser control circuit board, a signal generative circuit board, a lock-in amplified board, a data acquisition card, a control module, a multi-channel analog signal selection switch and a driving circuit are arranged in the main case of the monitor, the main case is connected with miniature optical sensors in various underground detection optical path through dingle mode fibers. The wavelength modulation of a gas laser absorption spectrum is realized by a low frequency scanning signal and a high frequency modulation signal generated by a signal generative circuit. The laser wavelength shift is carried out adaptive adjustment by the built-in gas calibration pond so as to realize the locking of a methane absorption line. The distributed multi-point methane concentration monitoring in the underground coal mine is realized by the switching of the multi-channel analog signal selection switch.

The invention discloses a fire scene multi-parameter laser wavelength modulation spectrum detection method and a device thereof, wherein, fire smoke products are treated through a smoke pre-treatment device and then pumped into a white cell through an air extracting pump; a multi-channel laser controller scans and modulates the wavelengths of a plurality of DFB lasers according to the time-sharing and multiplexing working mode, and all waves of laser share an optical fiber and are outputted sequentially through a wave combiner, then are aligned by a fiber collimator and sent to the white cell to detect the fire smoke products; a photoelectric detector converts light intensity signals of laser repeatedly reflected and absorbed by the white cell into electrical signals which are sent to two phase-locking magnifier modules for frequency selecting magnification so as to obtain a fundamental frequency component and a second harmonic component; a multi-channel data acquisition card converts output voltage signals of the phase-locking magnifiers into digital signals which are sent to a micro-computer for real-time data processing, so that the fire scene multi-parameter information containing the oxygen concentration of the fire scene, concentrations of various toxic gases and smoke concentration is obtained. The detection method and device can realize real-time on-line monitoring to fire scene multi-parameters, and have the advantages of being real-time, multi-component and highly sensitive, good selectivity of gas, high reliability and strong environmental disturbance resistance ability.

An FM-NMOR magnetometer and concomitant magnetometry method comprising providing a linearly-polarized pump beam generator, employing a center wavelength approximately equal to a center wavelength of hyperfine peaks, and employing a modulation amplitude in the range HFS-3×LW to HFS.

The invention discloses mid-infrared spectroscopy-based trace gas detection method and device combining a long-optical-path open light path with a wavelength modulation technique. The detection device mainly consists of a continuous wave quantum cascade laser (CW-QCL), a laser driving and controlling unit, a plane mirror, a beam splitter, a visible laser, a reference gas pool, mercury, tellurium and cadmium (MCT) detector, an off-axis parabolic mirror, a corner reflector, a digital lock-in-amplifier and a computer. By using the CW-QCL as a light source, long-optical-path open light path is combined with the wavelength modulation technique to detect multi-component trace gas with high sensitivity.

The invention relates to a gas temperature and concentration online measuring method based on a first harmonic signal, which belongs to the technical field of tunable diode laser absorption spectrum (TDLAS). Online measurement of the gas temperature and concentration is realized through the relation between a first harmonic X-axis signal and a first harmonic Y-axis signal and a gas absorption rate functional integral value. The advantages of a direct absorption method in the TDLAS technology are combined with the wavelength modulation method, so that not only is the difficulty that the direct absorption method cannot be applied in a worse environment and a weak absorption condition solved, but also the difficulty that the gas temperature and the gas concentration are determined through a calibration experiment in the measurement of the wavelength modulation method can be solved. Due to the adoption of the method, the measurement precision of the TDLAS technology in the industrial field can be effectively improved, and the application range can be enlarged.

The invention discloses a multi-component real-time online remote monitoring device and a method for coal spontaneous combustion indicator gas. For the limit of long distance optical fiber sensing band, the near-infrared band with weaker gas absorption line strength is used for real-time online monitoring the typical alkane gas as CO, CO2, C2H2 and C2H4 in the indicator gas. The multi-component weak signal is detected through the multi-frequency wavelength modulation and novel long optical distance multiple reflection pool technology; the device comprises a laser, a laser controller, a signal generator, a novel multiple reflection pool, an optical fiber collimator, a light beam coupler, a photoelectric detector, a lock-in amplifier, a processing system collecting the signal of A/D and terminal and an anti-explosion case. The device adopts the optical fiber for connection without manpower sampling, the responding sensitivity is high, the device and the method can monitor a variety of indicator gases at the same time with simple operation, good stability and small power, the device is easy to carry and install for field experimentation and the dynamic measuring range is large.

The invention relates to a device, a method and a system for determining a road surface condition, where the surface condition is one of dry, wet or icy. The device comprises a reflectance spectrometer which senses the reflectance properties of the road at one or several wavelengths and uses these reflectance properties to determine the surface condition. The reflectance spectrometer is a wavelength modulation spectrometer, preferably for the near infrared region. The system determines the surface condition and indicates it to a user of the system.

There is provided a glucose monitoring method and apparatus based on the principle of Wavelength-Modulated Differential Laser Photothermal Radiometry (WM-DPTR). Two intensity modulated laser beams operating in tandem at specific mid-infrared (IR) wavelengths and current-modulated synchronously by two electrical waveforms 180 degrees out-of-phase, are used to interrogate the tissue surface. The laser wavelengths are selected to absorb in the mid infrared range (8.5-10.5 μm) where the glucose spectrum exhibits a discrete absorption band. The differential thermal-wave signal generated by the tissue sample through modulated absorption between two specific wavelengths within the band (for example, the peak at 9.6 and the nearest baseline at 10.5 μm) lead to minute changes in sample temperature and to non-equilibrium blackbody radiation emission. This modulated emission is measured with a broadband infrared detector. The detector is coupled to a lock-in amplifier for signal demodulation. Any glucose concentration increases will be registered as differential photothermal signals above the fully suppressed signal baseline due to increased absorption at the probed peak or near-peak of the band at 9.6 μm at the selected wavelength modulation frequency. The emphasis is on the ability to monitor blood glucose levels in diabetic patients in a non-invasive, non-contacting manner with differential signal generation methods for real-time baseline corrections, a crucial feature toward precise and universal calibration (independent of person-to-person contact, skin, temperature or IR-emission variations) in order to offer accurate absolute glucose concentration readings.

Methods and systems to measure simultaneously concentrations or concentration ratio(s) of two or more gas ingredients in a sample area comprising: a wavelength modulated light source; an acoustic detector or a photodetector; and means to analyze the signal from the acoustic detector or the photodetector and calculate the concentrations or concentration ratio(s). The light from the light source is transmitted through the sample area. Part of the light will be absorbed in the sample area by the gas ingredients and generates photoacoustic signal. The acoustic detector is used to sample the photoacoustic signal. Alternatively, a photodetector is used to sample the light intensity after the light is transmitted through the sample area.

The invention discloses a pulse wavelength modulation (PWM) generator based on field programmable gate array (FPGA). The generator comprises an FPGA, wherein the FPGA is loaded with a decoding interface unit, a triangular carrier generating unit and n PWM signal generating units. The novel PWM signal generator disclosed by the invention can be realized by combining with FPGA hardware programming language and FPGA circuit design software tool, so as to better solve the problem in a high-power electronic system that the precision is affected since computation is heavy and digital control is delayed due to multiple paths of PWM signals; the carrier frequency, the dead time and the enable signal can be designed according to demands of the system, and the application range is wide and flexible application to various situations is realized; and meanwhile, the PWM generator still has the advantages of high reliability, reduced hardware design cost, strong antijamming capability and the like when being applied to other PWM signal generating circuits.

The new type nodal real-time gas densitymonitoring method and sensor has one near infrared DFB semiconductor laser and operates on the characteristic absorption of methane in the near infrared spectrum region. One monomode fiber power coupler is used in separating the laser beam into several beams led through fibers to fiber gas absorption cells in mine, and the laser beams through the absorbed gas are then led through fiber to the input optical switch. The selected signal through the calibrating cell is projected to the laser detector. By means of wavelength modulating technology and second harmonic detecting technology, the present invention realizes gas density measurement in high sensitivity, high resolution, no gas interference and fast response. Background light strength signal fitting method is adopted to eliminate the influence of light strength fluctuation on the measurement.

Methods of controlling semiconductor lasers are provided where the semiconductor laser generates a wavelength-modulated output beam λ_MOD that is directed towards the input face of a wavelength conversion device. The intensity of a wavelength-converted output λ_CONV of the device is monitored as the output beam of the laser is modulated and as the position of the modulated output beam λ_MOD on the input face of the wavelength conversion device is varied. A maximum value of the monitored intensity is correlated with optimum coordinates representing the position of the modulated output beam λ_MOD on the input face of the wavelength conversion device. The optical package is operated in the data projection mode by directing an intensity-modulated laser beam from the semiconductor laser to the wavelength conversion device using the optimum positional coordinates. Additional embodiments are disclosed and claimed. Laser controllers and projections systems are also provided.

Distributed fiber optic sensor includes a composite support tube that closely matches the coefficient of thermal expansion of the optical sensing fiber contained therewithin for applications including but not limited to Rayleigh back-scattering, (OFDR, Optical Frequency Domain Reflectometry), Brillouin frequency shift (BOTDA, Brillouin Optical Time Domain Analysis, BOTDR, Brillouin Optical Time Domain Reflectometry), Raman (Optical Time Domain Reflectometry), DPP-BOTDA (Differential Pulse Pair Brillouin Optical Time Domain Analysis), Dual-Index BOTDA, PCF (Photonic Crystalline Fibers), and dense packed Fiber Bragg Gratings, both time and wave length modulated are described in detail.

The invention discloses a system and a method for simultaneously monitoring multiple components of building fire early-stage characteristic gases. Characteristic gases (CO, CO2, C2H2 and HCN) released in a fire early-stage pre-combustion stage are simultaneously detected by adopting a tunable semiconductor laser absorption spectrum-based modulation frequency multiplexing technique; the influence on a measuring result caused by light intensity fluctuation due to gas disturbance in a laser light source and a light path is eliminated by adopting a self-balancing detection technique, and high detection sensitivity is obtained by combining a wavelength modulation technique, and multiple components of the building fire early-stage characteristic gases are simultaneously detected by using a multi-wavelength, self-balancing detection and frequency division multiplexing-based signal detection technique.

A chemical analysis method for determining the concentration of carbon monoxide, gaseous water and gaseous hydrocarbon in a combustion gas. The method includes the following steps: (a) directing wavelength modulated light from a single tunable diode laser at a wavelength in the range of from 2 to 2.5 micrometers through the combustion gas to a light detector to produce an absorption profile of the combustion gas (b) digitizing the adsorption profile of the combustion gas; (c) storing the digitized adsorption profile in a digital computer; (d) processing the digitized adsorption profile in the digital computer to produce an output from the computer indicative of the concentration of carbon monoxide, gaseous water and gaseous hydrocarbon in the combustion gas.

The invention discloses a method for realizing optical zooming, that is, an optical zoom method based on a super-structured lens using wavelength modulation, based on (1) a light source probe, (2) linear polarizing plates, and (3) quarter wave plates, (4) a super-structured (chromatic aberration) lens; the super-structured (chromatic aberration) lens (4) is placed in the middle of two combinationsof the linear polarizing plates and the quarter wave plates, and a photoreceptor (5) is disposed on the imaging surface for receiving images; and incident light of different wavelengths is used to pass through a super-structured (chromatic aberration) lens for imaging at different image distance positions for zooming. There are two kinds of application scenarios: one is that the image distance isfixed, the illumination wavelength and the object distance are adjusted to obtain the change of the size of the imaging image; the second is that the object distance is fixed, and the illumination wavelength and the image distance are adjusted to obtain the change of the imaging size. The method adopts the design principle of the super-structured surface, the chromatic aberration is controlled bythe phase matching, and the spherical aberration and the coma aberration correction can be performed within a certain imaging interval.