Detector bandwidth

FIGURE 5.7 FM CARS signal versus dilution factor, n. / is the FM CARS signal intensity frommethanoldissolvedin water, while/, 3x the CARS signal intensity from a pure methanol sample. Filled circles represent the experimental data points taken at a detector bandwidth of 25 kFlz. Open circles correspond to data taken when the detector bandwidth was set to 1.6 Flz. The solid line is a plot of Equation 5.2. 

Lower-speed ADC and lower-level processor It transmits a series of bursts of narrowband pulses where each burst is a sequence consisting of many pulses shifted in frequency from pulse to pulse with a fixed frequency step. Each received narrow-band pulse is phase detected and then combined into the large effective bandwidth (sequentially over many pulses). Therefore, the hardware requirement is less stringent relative to that of UWB-IR. The detector bandwidth is smaller, resulting in lower noise bandwidth and higher signal-to-noise (SN) ratio when compared with UWB-IR. 

Fig. 14.3 Typical spectral profiles of a tungsten halogen, b deuterium, c eompaet eontinuous Xe arc, d low pressure and e medium pressure Hg lamps reeorded with an Oeean Opties calibrated spectrometer. Note that the speetra are each individually ntnmalised to a maximum of 1 and comparison of relative intensities between lamps cannot be made. Note also that when using a detector bandwidth wider than the emission line bandwidth, the measured relative intensities of lines eompared to continuum varies with detector bandwidth, with the ratio of line-emission to continuum increasing with decreasing bandwidth. The lower panel shows photographs of commonly encountered lamps i a variety of tungsten lamps, ii deuterium, iii compact xenon, iv a short arc xenon arc and v super pressure mercury lamp. The 5p UK coin, included to give some idea of scale, has a diameter of 18 mm...

From the point of view of this work the main parameters are specific detectivity and the detector bandwidth. It is especially convenient to use a synthetic parameter obtained by multiplying the specific detectivity with the bandwidth. Specific detectivity unites sensitivity or quantum efficiency with noise equivalent power. Thus, the D f product describes all fundamental limitations of a detector, taking into account both its behavior at high operating frequencies and at low signal intensities. 

The detectivity D [cm/s / -W ] gives the obtainable signal-to-noise ratio Vg/Vn of a detector with the sensitive area A and the detector bandwidth Af, at an incident radiation power of P = 1 W. Because the noise equivalent input power is NEP = P V /Vg the detectivity of a detector with the area 1 cm and a bandwidth of 1 Hz is D = 1/NEP. 

The detectivity D gives the obtainable signal to noise ratio V /V, multiplied by the square root of detector area A and, detector bandwidth Af and divided the incident radiation power P. 

The Pr EN 12668-1 concerns the verification of characteristics of ultrasonic flaw detector. It is mainly applicable to portable equipment incorporating Ascan visualisation on screen, and which bandwidth is comprised between 0,5 and 15 Mhz. The project describes three levels of verification ... 

The amplified signal is passed to a double-balanced mixer configured as a phase-sensitive detector where the two inputs are the NMR signal (cOq) and the frequency of the synthesizer (03. gf) with the output proportional to cos(coq - co gj.)t + 0) + cos((coq + + 9). The sum frequency is much larger than the total bandwidth of the... 

Radiation exits the monochromator and passes to the detector. As shown in Figure 10.12, a polychromatic source of radiation at the entrance slit is converted at the exit slit to a monochromatic source of finite effective bandwidth. The choice of... 

The NEP may be written in terms of the detector element active area, the number of detector pixels elements cormected for additive output the electronic noise bandwidth B and the detector element detectivity, D. Typically = 1, but may be increased for improved sensitivity with an attendant loss in resolution. 

Fig. 4. Sensitivity for the detection of CO using spectral thermography as a function of absorbing path length. Detector NEP = 30 pW, J = 1.0 mW/cm, A = 1.5E — 5 cm, samples = 60, number of detectors = 600, G = 6.6E5 ppm-cm center wavelength = 4.65 /im spectral bandwidth = 0.2 fim.

Detectors aie all intrinsic unless otherwise noted. See Fig. 1. Visible bandwidth near infrared = 0.700-1.00 fim. 

Detectivity. Detector sensitivity (1,2) is expressed in terms of the minimum detectable signal power or noise equivalent power (NEP) given in units of watts or W. The reciprocal function when normalized for detector area, M, and noise bandwidth, is defined as detectivity, D, in units of /W. Thus,... 

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