Spectroscopic imaging device employing imaging quality spectral filters

Abstract

Techniques for providing spectroscopic imaging integrates an acousto-optic tunable filter (AOTF), or an interferometer, and a focal plane array detector. In operation, wavelength selectivity is provided by the AOTF or the interferometer. A focal plane array detector is used as the imaging detector in both cases. Operation within the ultraviolet, visible, near-infrared (NIR) spectral regions, and into the infrared spectral region, is achieved. The techniques can be used in absorption spectroscopy and emission spectroscopy. Spectroscopic images with a spectral resolution of a few nanometers and a spatial resolution of about a micron, are collected rapidly using the AOTF. Higher spectral resolution images are recorded at lower speeds using the interferometer. The AOTF technique uses entirely solid-state components and requires no moving parts. Alternatively, the interferometer technique employs either a step-scan interferometer or a continuously modulated interferometer.

Description

FIELD OF THE INVENTIONThe present invention relates to devices used for spectroscopic imaging, and more particularly to devices that non-invasively and rapidly collect images of a sample at multiple, discrete wavelengths in the ultraviolet, visible, near-infrared and infrared regions of the optical spectrum. The character of the images recorded is determined by a sample's chemical characteristics as revealed by its intrinsic electronic and vibrational absorptions or emissions.BACKGROUND OF THE INVENTIONSpectroscopic imaging can be used to determine the spatially distributed and chemically distinct species in heterogenous materials. Spectroscopic imaging is an analytical tool that has been applied at both the macroscopic and microscopic levels.At the macroscopic level, chemical imaging of areas exceeding 20 square kilometers can be achieved using airborne and spaceborne remote sensing, near-infrared imaging spectrometers. On a smaller scale, diagnostic imaging of the human body is po...

AI Technical Summary

Benefits of technology

Accordingly, a general object of the present invention is to provide devices for rapidly filtering light sources in the ultraviolet, visible, near-infrared and infrared regions of the optical spectrum for utilization in absorption microscopy while retaining image fidelity. Another general object of the present invention is to provide devices for spectrally filtering emitted radiation from samples encountered in emission microscopy, specifically fluorescence and Raman microscopy, while retaining image fidelity.

Yet another object of the present invention is to provide the ability to collect spectroscopic data sets and manipulate the data sets to reveal the precise molecular arrangements of the samples analyzed, including particularly subtle molecular arrangements not easily determinable by other analytical imaging techniques.

An advantage to the present invention includes the ability to rapidly and simultaneously record and analyze thousands of absorption spectra with diffraction limited spatial resolution and high spectral resolution.

Problems solved by technology

Scanning methods for vibrational spectroscopic imaging, while workable, have certain drawbacks and deficiencies.

Specifically, the signal to noise ratios obtainable with FTIR microspectrometers often requires substantial signal averaging at each spatial position, thus making the FTIR systems inherently slow.

Furthermore, the numerous moving parts contained within these systems limit the speed and reliability of these devices.

Wide field illumination methods employing glass or interference filters, however, have certain drawbacks and deficiencies.

Specifically, the application of discrete notch filters for spectral selectivity requires the use of a separate filter at each desired wavelength, ultimately limiting operation to only several wavelengths.

In addition, the dielectric notch filters employed provide resolution of approximately 10-100 nm, which is often an inadequate spectral resolution for discriminating similar but different species in multicomponent environments.

The techniques using filter wheels provide only limited spectral resolution and spectral coverage, and also suffer from the constraints of moving mechanical parts, limiting the speed and reliability of these systems.

The multichannel / spatial multiplex method, however, also has certain limitations.

Where survey spectral images are to be collected, the Hadamard imager is not optimal.

In addition, artifacts can arise in the spectral images due to systematic spatial encoding errors.

These artifacts ultimately compromise the spatial resolution of the technique.

Images