Optical instruments, calibration

Hilsenrath, E., D. Williams and J. Frederick (1988) Calibration of long term data sets from operational satellites using the space shuttle. Society of Photo-Optical Instrumentation and Engineering Proceedings 924 215-222. 

The analyst uses ICP-OES (inductively coupled plasma, optical emission spectroscopy) to measure twenty different metal ions in solution. To fully calibrate the instrument requires the preparation and measurement of 100 individual calibration standards (five point calibration per element). It would be impracticable for an analyst to calibrate the instrument daily. The instrument is calibrated at regular intervals (say fortnightly) by the analyst. In the intervening time, the calibration for each metal ion is checked by the use of a set of drift correction standard solutions. Minor corrections can then be made to the calibration to allow for day-to-day drift. 

Sped roscope Optical instrument for producing and analysing a spectiTjm of the light emitted from a source. A calibrated spectroscope is known as a spectrometer. 

In recent years great advance has been made in instrumentation for ORD and, in particular, for CD measurements [see, for example, Refs. (32—39,17)]. The improvements in measurement of CD within an absorption band enabled progress in the determination of the optical activity of conjugated protein molecules, particularly for systems of relatively small activity. A frequently used calibration substance for CD instruments is (+)-camphor-10-sulfonic acid in aqueous solution. In order to achieve correct calibration, optical rotation values of the calibration substance should be transformed to CD values used for standardization (40, 41). 

The ideal situation for a process analyzer is to have the detector/electrical components in an area physically isolated from the sample stream and any liquid components required for calibration or instrument operation (e.g., solvents for liquid chromatography or gel-permeation chromatography). In this arrangement, isolation of the electrical components ensures that a spark source or hot surface (such as a spectroscopic light source) will not cause a problem with flammable components (both sample stream components and solvents). Also, this isolation wiU limit instrument damage in case of a sample system leak or solvent leak. Although the ideal situation is often not realized in a practical application, one should make every effort to protect the delicate sections of the instrument. In one application of the authors, a fiber optic probe having a quartz window sealed on the end of the probe was installed in the reactor of a process that contained... 

The knowledge of the laws that govern celestial phenomena the discoveries of mathematical analysis, leading to more exact methods of calculating those phenomena the perfection beyond all expectation attained by optical instruments and instruments whose precise calibration determines the precision of the observations made with their help the... 

M.R. Bolcar, D.T. Leisawitz, S.F. Maher, S.A. Rinehart, Demonstration of the wide-field imaging interferometer testbed using a calibrated hyperspectral image projector, in Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, vol. 8445 (2012)... 

In the common understanding of calibration, the calibration procedure may involve the measurement of some reference material whose size has been carefully determined and verified by other reference techniques, and the instrument s calibration constant will be adjusted to match the assayed value. However, since laser diffraction is an absolute measurement technology it is not required to use reference materials to calibrate the instrument, although one may use these materials to verify the validity and status of an instrument. For a laser diffraction analyzer, calibration is mainly related to the alignment of the optics (i.e., the laser and detectors). Since in most cases the detectors are etched onto a circuit board they are not individually mobile components. The task then is simply to align the laser, the focusing lens, and the detector array. 

Cetinic, L, Toro-Farmer, G., Ragan, M., Oberg, C., and Jones, B.H. (2009). Calibration procedure for Slocum glider deployed optical instruments. Opt. Express, 17,15420-15430. 

A Q-switched, frequency-quadrupled Nd—YAG laser (X, = 266 nm) and its accompanying optical components produce and focus the laser pulse onto the sample surface. The typical laser spot size in this instrument is approximately 2 pm. A He-Ne pilot laser, coaxial with the UV laser, enables the desired area to be located. A calibrated photodiode for the measurement of laser energy levels is also present... 

An ICP-OES instrument consists of a sample introduction system, a plasma torch, a plasma power supply and impedance matcher, and an optical measurement system (Figure 1). The sample must be introduced into the plasma in a form that can be effectively vaporized and atomized (small droplets of solution, small particles of solid or vapor). The plasma torch confines the plasma to a diameter of about 18 mm. Atoms and ions produced in the plasma are excited and emit light. The intensity of light emitted at wavelengths characteristic of the particular elements of interest is measured and related to the concentration of each element via calibration curves. 

Pyrolysis spectra become distorted with respect to their diagnostic features for two major sets of reasons. The first is variations in instrument operation (e.g., heat transfer efficiency from wire to sample, ion source temperature, MAB gas identity, analyzer calibration, tuning, and ion transmission discrimination attributable to contaminated optics). Most of these factors can be controlled... 

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