Spectrometers for Imaging Applications
Dispersive spectrometers image spectra; that is their function. Imaging the spectrum is required to resolve discrete wavelengths. The spectrum is a one-dimensional dataset originating from one discrete point in a source. While we presumably always want a spectrum from a spectrometer, we may also want more. We might want to collect spectra for several sources simultaneously, for example. Alternatively, several regions in one source might be of interest. These days, an instrument capable of imaging both spectral and spatial features of source is called an imaging spectrometer.
While almost all spectrometers do a good job of imaging spectra, they may not always be spatially discriminating. With some adjustment to the optics, spatial sensitivity can improve. It is likely that light through put and possible that spectral resolution will be compromised. Still, it is often efficient to multiplex spectrometers capabilities. In addition, when the spectrometer provides a 1:1 image, flux per pixel is improved. This is helpful in spectroscopy applications like Raman, luminescence or LIBS. It is also helpful when spectral investigation of spatially distinct sources or events is required. This might the changing spectra across a candles flame or a thermonuclear fusion experiment.
Development and use of novel optics in McPherson instruments improves imaging and suits two-dimensional CCD, CMOS and intensified detectors. No optical system is perfect, and the best choice of optics depends totally on the needs of the experiment. Balancing cost, complexity, surface quality, imaging performance, and spectral resolution, requires serious consideration before making an investment in a research-grade spectrometer.
Imaging Spectrometer Applications
The pictured one meter McPherson spectrometer can simultaneously monitor spectra from 100 input fibers on one commercial 1024*1024 pixel, ~13mm square CCD. Sub Angstrom spectral resolution is attained in all channels. The spectrometer accepts various diffraction gratings that may be optimized for spectral resolution or for wavelength range coverage. With sensitive, cooled CMOS or CCD detectors, the accessible 50mm focal plane is ideally suited for simultaneously intercepting and analyzing multiple spectra from spatially distinct regions.
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Please refer to the Spectrometers for Imaging Applications PDF. Thank you.
