Abstract
The spectral content of a sample provides important information that cannot be detected by the human eye or by using an ordinary RGB camera. The spectrum is typically a fingerprint of the chemical compound, its environmental conditions, phase and geometry. Thus measuring the spectrum at each point of a sample is important for a large range of applications from art preservation through forensics to pathological analysis of a tissue section. To date, however, there is no system that can measure the spectral image of a large sample in a reasonable time. Here we present a novel method for scanning very large spectral images of microscopy samples even if they cannot be viewed in a single field of view of the camera. The system is based on capturing information while the sample is being scanned continuously 'on the fly'. Spectral separation implements Fourier spectroscopy by using an interferometer mounted along the optical axis. High spectral resolution of ~5 nm at 500 nm could be achieved with a diffraction-limited spatial resolution. The acquisition time is fairly high and takes 6-8 minutes for a sample size of 10mm x 10mm measured under a bright-field microscope using a 20X magnification.
Highlights
Spectral imaging combines spectroscopy with imaging, two widespread methodologies, generating advantages that cannot be obtained separately by imaging or spectroscopy alone
A similar optical concept was described for measuring the near infrared (NIR) spectral image in remote sensing [18] that emphasized the NIR spectral range, the remote sensing application and the light radiation parameters, but measuring large images at a high speed for a microscopy setup was not treated
We presented a spectral imaging system based on a new optical concept that can measure the spectral images of very large samples, which cannot be observed by a single field of view of a camera
Summary
Spectral imaging combines spectroscopy with imaging, two widespread methodologies, generating advantages that cannot be obtained separately by imaging or spectroscopy alone. At the end of the acquisition process, the set of images contains the interferograms for all the pixels and the data are processed to provide the spectral image This method requires an optical setup, which in addition to the optics contains a mechanical motor to rotate the interferometer and the controllers. To achieve a much shorter acquisition time and to overcome these problems, we describe a new method for rapid measurements of large spectral images It is based on Fourier spectroscopy designed for measuring very large samples that cannot be captured by a single. At the end of the measurement, the intensities that were measured for each sample point through different OPDs are collected to form the interferogram (Fig. 3), which is Fourier transformed to get the spectrum of each sample point This method is highly compatible with microscopy systems that typically have a computer-controlled scanning stage. A similar optical concept was described for measuring the near infrared (NIR) spectral image in remote sensing [18] that emphasized the NIR spectral range, the remote sensing application and the light radiation parameters, but measuring large images at a high speed for a microscopy setup was not treated
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