Acousto-optical tunable filters AOTFs

Acousto-optic Filters. The newest type of spectrometer to become commercially available is the acousto-optic tunable filter (AOTF). An AOTF is a sohd-state, electronically tunable bandpass filter based on the diffraction of optical waves by acoustic waves in an optically anisotropic crystal. 

The acousto-optic tunable filter (AOTF) analyzer... 

There are several measurement techniques that can be considered for use in IR-based instrumentation in the NIR and the mid-IR spectral regions, and these are summarized in Table 4.1. Some of these techniques are classical, as in the case of optical filter-based instruments and scanning monochromators. Others, such as acousto-optically tunable filter (AOTF), have been considered for 15+ years, but are mainly applied to NIR... 

Wang, X. Soos, J. Li, Q. 8t Crystal, J., An Acousto-Optical Tunable Filter (AOTF) NIR Spectrometer for On-line Process Control Process Contr. Qual. 1993, 5, 9-16. 

Fig. 1 Schematic drawing of a wide-field single-particle tracking fluorescence microscope equipped. Several lasers are used as excitation source for different fluorophores with fast selection hy an acousto-optical tunable filter (AOTF). The collimated laser light is coupled into the objective such that only the observed area is illuminated. The emission light is separated from the excitation light by a dichroic mirror. In the case of multi-color imaging, the emission light is separated by...

A modification of the Debye-Sears effect, i.e., the modulation of the refractive index by acoustical waves functioning as tunable grating, is now applied to fast scanning NIR spectroscopy The Acousto-Optic Tunable Filter (AOTF), (Harris and Wallace, 1969 Chang, 1981). In combination with array detectors, chemical imaging is possible (Treado et ah," 1992). 

Figure 9.1. Schematic of Raman spectrometer based on an acousto-optic tunable filter (AOTF). BP, bandpass filter BR, band reject filters APD, avalanche photodiode. (Adapted from Reference 9, with permission.)...

Acousto-optic tunable filters (AOTF) are solid-state, rapidscanning instruments. The heart of the instrument is an anisotropic crystal (Fig. 4) capable of splitting a particular wavelength of light into its ordinary and extraordinary (clockwise and counter-clockwise rotated) rays. One face (orthogonal to the light beam) has a transducer bonded to it. 

In one paper by Kirsch and Drennen [62], three experiments were performed on coated tablets. In the first experiment, intact theophylline tablets coated with an ethylcellulose polymer were analyzed by acousto-optic tunable filter (AOTF) spectrometers. Tablets were coated with increasing levels of ethylcellulose to vary the dissolution profiles. After spectra were collected, the dissolutions were run on a U.S.P. Type II dissolution apparatus. The time required for 50% of the drug to enter solution was used as the measure of dissolution rate. Principal component (PC) regression was used to develop the calibration. This gave a SEE of 2.8 min, a coefficient of variation of 0.977, and a SEP of 6.6 min the time to 50% dissolution ranged from 48 to 93 min. 

Keywords Hyperspectral imaging spectropolarimetric imaging acousto-optic tunable filter AOTF ... 

DEVELOPMENT OF MINIATURE ACOUSTO OPTIC TUNABLE FILTER (AOTF) SPECTROMETER FOR DETECTION OF TOXIC INDUSTRIAL... 

AOTF. An acousto-optical tunable filter (AOTF) (53) is a radio frequency (RF)-controlled narrow-band interference filter. Figure 4.1.10 is a schematic of a typical AOTF spectrometer. Most contemporary AOTF crystals are tellurium dioxide (TeOa)... 

Determination of properties of film coated tablets was demonstrated by Kirsch and Drennen [73] in 1995. Here, the thickness of an ethylcellulose coating, T50 (50% dissolution time), and the hardness of the tablet were determined from NIR spectra measured on grating based and acousto-optic tunable filter (AOTF) specfiometers. While the performance of the grating based spectrometer was superior, the AOTF was demonstrated to perform adequately for most pharmaceutical applications and had the advantage of substantially shorter measurement times. This demonstration of the capacity for rapid tablet analysis was a critical step towards the implementation of such systems in an in-line tablet analysis system. 

Although the 75 ms acquisition time is a significant improvement over laboratory-based collection times, some conveyer speeds may require a faster collect time. A second prototype, not detailed here, incorporated acousto optical tunable filter (AOTF) technology that allowed faster, and more selective data collection. 

Acousto-optic tunable filter (AOTF)-based Brimrose (Baltimore, MD), Infrared Fiber Systems (Silver Springs, MD). 

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