Resolution signal-to-noise

The spectra of adsorbed and surface species obtained using transmission and DR techniques are very similar in quality, in regard to resolution, signal-to-noise ratio and sensitivity. 

Recently, photon counting has become an important technique in spectro-photometric methods where the radiation is so low in intensity that it is difficult to obtain measurements by conventional means. The ability to deal with low radiation levels with a satisfactory signal-to-noise ratio is of course one of the important factors in the photon-counting method. Improvements in precision, resolution, signal-to-noise ratio, and readout are obtainable by photon counting, and this method should be applicable to all spectrophotometric procedures (absorption, emission, reflection, fluorescence, and light scattering) in which a photomultiplier is used. 

Basic spectroscopic measurements involve the instrumental concepts of bandpass and resolution, signal-to-noise ratio, dynamic range, stray light, wavelength accuracy and precision, and photometric accuracy and precision. These concepts were described in Chapter 1. 

Acquisition and Processing of Data of Adequate Quantity and Quality (e.g., energy resolution, signal-to-noise ratio, scan widths required for background subtraction, etc.)... 

The detectability of critical defects with CT depends on the final image quality and the skill of the operator, see figure 2. The basic concepts of image quality are resolution, contrast, and noise. Image quality are generally described by the signal-to-noise ratio SNR), the modulation transfer function (MTF) and the noise power spectrum (NFS). SNR is the quotient of a signal and its variance, MTF describes the contrast as a function of spatial frequency and NFS in turn describes the noise power at various spatial frequencies [1, 3]. 

So, a comparison of different types of magnetic field sensors is possible by using the impulse response function. High amplitude and small width of this bell-formed function represent a high local resolution and a high signal-to-noise-characteristic of a sensor system. On the other hand the impulse response can be used for calculation of an unknown output. In a next step it will be shown a solution of an inverse eddy-current testing problem. 

Composite transducers will replace conventional transducers in applications where the improvement of test sensitivity, signal to noise ratio and axial resolution are mandatory. It must nevertheless also be noted in connection with the broadband feature that though composite probes have a specified nominal frequency, the echo signals allow no echo amplitude... 

The VMOS-pulser with a rise time lower than 6 ns provides high axial resolution and high-frequency inspections above 10 MHz with an excellent signal-to-noise ratio. The output voltage amounts to about 228 V without load, and 194 V with a load of 75 H, A damping control from 75 Q to 360 Q matches the impedance to the transducer. 

The spatial resolution of the CI SEM mode depends mainly on the electron-probe size, the size of the excitation volume, which is related to the electron-beam penetration range in the material (see the articles on SEM and EPMA), and the minority carrier diffusion. The spatial resolution also may be afiFected by the signal-to-noise ratio, mechanical vibrations, and electromagnetic interference. In practice, the spatial resolution is determined basically by the size of the excitation volume, and will be between about 0.1 and 1 pm ... 

---