Dennis M. Hueber

Fast Scanning Synchronous Luminescence Spectrometer Based on Acousto-Optic Tunable Filters:

A new luminescence spectrometer based on quartz-collinear acousto-optic tunable filters (AOTFs) and capable of synchronous scanning is described. An acousto-optic tunable filter is an electronically tunable optical bandpass filter. Unlike a tunable grating monochromator, an AOTF has no moving mechanical parts, and an AOTF can be tuned to any wavelength within its operating range in microseconds. These characteristics, combined with the small size of these devices, make AOTFs an important new alternative to conventional monochromators, especially for portable instrumentation. The relevant performance of the AOTFs (efficiency, bandwidth, rejection, etc.) is compared with that of typical small-grating monochromator.

Laser-Induced Solid-Surface Room-Temperature Phosphorimetry of Polycyclic Aromatic Hydrocarbons

Laser-induced solid-surface room-temperature phosphorimetry (SSRTP) has been employed for the detection of polycyclic aromatic hydrocarbons. A nitrogen-pumped laser and a dye laser were used as excitation sources. The effects of sample volume, laser irradiation, and background reduction treatment on the precision and sensitivity of the method were studied. With the use of thallium(I) acetate as a phosphorescence enhancer, picogram limits of detection were estimated for phenanthrene, pyrene, benzo[g,h,i]perylene, chrysene, coronene, and 1,2-benzofluorene. The study demonstrates that laser excitation can improve the sensitivity of SSRTP by up to three orders of magnitude.

Remote spectral imaging system (RSIS) based on an acousto-optic tunable filter (AOTF)

Abstract This paper describes a new remote spectral imaging system (RSIS) based on an acousto-optic tunable filter (AOTF) capable of remote sensing using an imaging fiberoptic probe (IFP). A two-dimensional charge coupled device (CCD) was used as a detector. The AOTF was used as a wavelength selector. Unlike a tunable grating or prism based monochromator, the tunable filter has no moving parts, and it can be rapidly tuned to any wavelength in its operating range. The large aperture of the AOTF and its high spatial resolution allowed the optical image from an IFP to be recorded by a CCD. These characteristics, combined with their small size, make AOTFs important new alternatives to conventional monochromators, especially for spectral multisensing and imaging. A prototype RSIS system, using both IFP and AOTF, was developed and its feasibility for spectral imaging was demonstrated.

Phosphorescence imaging system using an acousto-optic filter-based charge coupled device

Abstract We are reporting for the first time the development of an imaging spectrometer for solid surface room temperature phosphorimetry based on an acousto-optic tunable filter. A Heue5f8Cd laser was employed as the excitation source, and a cooled two-dimensional charge coupled device was used as the detector. The spectral characterization and imaging capability of the new system were evaluated with two well known phosphorescent compounds. The phosphorescence emissions of pyrene and 1,2,3,4-dibenzanthracene adsorbed on chromatography paper treated for background reduction were investigated. Thallium(I) acetate was employed as a phosphorescence enhancer. Based on the performance of the proposed instrument, several potential applications are discussed.

Fiber-Optic Remote Multisensor System Based on an Acousto-Optic Tunable Filter (AOTF)

This paper describes a new fiber-optic multisensor based on an acousto-optic tunable filter (AOTF) and capable of remote sensing using a multioptical fiber array (MOFA). A two-dimensional charge-coupled device (CCD) was used as a detector, and the AOTF was used as a wavelength selector. Unlike a tunable grating or prism-based monochromator, an AOTF has no moving parts, and an AOTF can be rapidly tuned to any wavelength in its operating range within microseconds. The large aperture of the AOTF allows the optical signal from over 100 fiber-optic sensors to be measured simultaneously. These characteristics, combined with their small size, make AOTFs an important new alternative to conventional monochromators, especially for spectral multisensing and imaging. A prototype fiber-optic multisensor system has been developed, and its feasibility for simultaneous detection of molecular luminescence signal via fiber-optic probes is demonstrated.

Analysis of Polycyclic Aromatic Compounds in Soil Samples Using Laser-Induced Phosphorimetry

Abstract The analysis and spectral characteristics of several polycyclic aromatic hydrocarbons (PAHs) have been investigated by Laser-Induced Solid-Surface Room Temperature Phosphorimetry (LI-SSRTP). These PAHs included phenanthrene, chrysene, 1,2 benzofluorene, 2,3 benzofluorene, pyrene, coronene, 1,2,3,4 dibenzanthracene, benzo(a)pyrene, benzo(e)pyrene, and benzo(g, h, i)perylene. A nitrogen laser was employed as the excitation source at 337 nm. Filter paper treated with UV irradiation for background reduction was used as the solid substrate. Thallium(I)acetate was employed as a phosphorescence enhancer. Absolute limits of detection in the picogram level were obtained for all the PAHs, improving SSRTP levels of detection by three orders of magnitude. Finally, the proposed method was tested with a PAH contaminated soil sample. Detection of several PAHs at the nanogram level was easily performed, showing the potential of LI-SSRTP to the analysis of samples of environmental concern.

Laser-Excited Synchronous Fluorescence System for the Analysis of Polycyclic Aromatic Compounds

Abstract We describe a laser-based synchronous luminescence (LSL) monitor developed for the detection of polycyclic aromatic compounds (PAC). With LSL the amount of sample pre-treatment can often be reduced and both the selectivity and sensitivity of the analysis can be increased by the high power and narrow profile of a laser source. A small, portable, pulsed dye laser was used in this study. The instrument and its application to the determination of PACs will be described. For comparison purposes, measurements using conventional synchronous luminescence of mixtures are also discussed.

Evaluation of Data Treatment Techniques for Improved Analysis of Fingerprint Images

We evaluated four different methods for data treatment of fingerprint images. The first two methods (Lees method, and Iterative Automated Noise Filtering method) are used to remove signal-independent additive noise from digital images of fingerprints. The two other methods (low-pass and high-pass wavelet filtering), based on the wavelet transform, are employed not only to reduce the noise, but also to enhance the information of the fingerprints, especially details at the ridges. To evaluate these four filtering techniques we analyzed images of various fingerprints provided by the Police Department of Knoxville, Tennessee, and recorded digitally in the laboratory using inexpensive apparatus. Experimental results show that the methods are effective in diverse cases and have potential in forensic analysis of fingerprints.

Multispectral imaging system using acousto-optic tunable filter (AOTF)

This paper describes the development of a multispectral imaging (MSI) device using AN acousto-optic tunable filter (AOTF). A 2D charge-coupled device (CCD) was used as a detector. The AOTF was used as a wavelength selector. Unlike a tunable grating or prism based monochromator, the tunable filter has no moving parts, and it can be rapidly tuned to any wavelength in its operating range. The large aperture of the AOTF and its high spatial resolution allowed the optical image from an IFP to be recorded by the CCD. These characteristics, combined with their small size, make AOTFs important new alternatives to conventional monochromators, especially for spectral imaging in biomedical applications.

Phosphorescence imaging system using an acousto-optic tunable filter and a charge-coupled device

Abstract We are reporting for the first time the development of an imaging spectrometer for solid-surface room temperature phosphorimetry based on an acousto-optic tunable filter. A HeCd laser was employed as the excitation source, and a cooled two-dimensional charge-coupled device was used as the detector. The spectral characterization and imaging capability of the new system were evaluated with two well known phosphorescent compounds. Thee phosphorescence emissions of pyrene and 1,2,3,4-dibenzanthracene adsorbed on chromatography paper treated for background reduction were investigated. Thallium(I) acetate was employed as a phosphorescence enhancer. Based on the performance of the proposed instrument, several potential applications are discussed.