Infrared signal amplifier

Air drawn through a vacuum pump into the gas cuvette of a nondispersive infrared spectrophotometer IR absorption by CO is measured using two parallel IR beams through sample and reference cell and a selective detector, detector signal amplified concentration of analyte determined from a calibration curve prepared from standard calibration gases (ASTM Method D 3162-91, 1993). 

Infrared pulses of 200 fs duration with 150 of bandwidth centred at 2000 were used in this study. They were generated in a two-step procedure [46]. First, a p-BaB204 (BBO) OPO was used to convert the 800 mn photons from the Ti sapphire amplifier system into signal and idler beams at 1379 and 1905 mn, respectively. These two pulses were sent tlirough a difference frequency crystal (AgGaS2) to yield pulses... 

In order to achieve a reasonable signal strength from the nonlinear response of approximately one atomic monolayer at an interface, a laser source with high peak power is generally required. Conuuon sources include Q-switched ( 10 ns pulsewidth) and mode-locked ( 100 ps) Nd YAG lasers, and mode-locked ( 10 fs-1 ps) Ti sapphire lasers. Broadly tunable sources have traditionally been based on dye lasers. More recently, optical parametric oscillator/amplifier (OPO/OPA) systems are coming into widespread use for tunable sources of both visible and infrared radiation. 

Collecting optics, radiation detectors and some form of indicator are the basic elements of an industrial infrared instrument. The optical system collects radiant energy and focuses it upon a detector, which converts it into an electrical signal. The instrument s electronics amplifies the output signal and process it into a form which can be displayed. There are three general types of instruments that can be used for predictive maintenance infrared thermometers or spot radiometers line scanners and imaging systems. 

Although astronomy is accustomed to the detection of a few photons per pixel, the electric charge of a few electrons is extremely small. A critical part of the design of a focal plane array is the amplifier which converts the small amount of charge in each pixel into a signal that can be transmitted off the detector. The amplifier in an optical or infrared detectors is typically a field effect transistor (FET), a solid state structure which allows a very small amount... 

A Fourier transform infrared spectroscopy spectrometer consists of an infrared source, an interference modulator (usually a scanning Michelson interferometer), a sample chamber and an infrared detector. Interference signals measured at the detector are usually amplified and then digitized. A digital computer initially records and then processes the interferogram and also allows the spectral data that results to be manipulated. Permanent records of spectral data are created using a plotter or other peripheral device. 

A photomultiplier tube is a sensitive detector of visible and ultraviolet radiation photons cause electrons to be ejected from a metallic cathode. The signal is amplified at each successive dynode on which the photoelectrons impinge. Photodiode arrays and charge coupled devices are solid-state detectors in which photons create electrons and holes in semiconductor materials. Coupled to a polychromator, these devices can record all wavelengths of a spectrum simultaneously, with resolution limited by the number and spacing of detector elements. Common infrared detectors include thermocouples, ferroelectric materials, and photoconductive and photovoltaic devices. 

In January 1992. E. Desurvire (Columbia University Center for Telecommunications Research) reported that optical fibers made from silica glass and traces of erbium can amplify light signals when they are energized by infrared radiation. Desurvire developed an efficient radiation source (referred (o as a laser diode chip) that, when integrated into a fiber optic communication system, can increase transmission capacity by a factor of 10(1. 

The CARS system used to measure temperature and species concentrations in the combustor zone is composed of a single-mode ruby-laser oscillator-amplifier with a repetition rate of 1 Hz and a ruby-pumped, near-infrared broad-band dye laser. The two laser beams are combined collinearly and focused first into a cell containing a nonresonant reference gas and then into the sample volume (approximately 30-u diam. x 2 cm) in the combustion region. The anti-Stokes beams produced in the sample and reference volumes are directed to spatially separated foci on the entrance slit of a spectrometer and detected by separate photomultiplier tubes. An optional means of detection is provided for the sample signal in the form of an optical multichannel analyzer (OMA), which makes it possible to obtain single-pulse CARS spectra. 

The next class of VCD instruments to be developed was centered around a Fourier transform infrared (FT-IR) spectrometer. The idea was to design the sample compartment to be the same as in a dispersive VCD instrument, including a photoelastic modulator. To measure VCD, the detector signal is first sent to a lock-in amplifier to demodulate the high-frequency polarization modulation. The output of the lock-in is a VCD interferogram which is Fourier transformed in much the same way as the ordinary transmission interferogram. 

In an infrared spectrometer equipped with a linear polarizer and a PEM the CD of the sample is then extracted from the detector signal by means of a lock-in amplifier tuned to the operating frequency of the photoelastic modulator. 

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