Systems
Spectrometers intended for very wide spectral ranges are best if made with all-mirror systems. These particular systems have no chromatic aberrations, and that is why they are preferable. On the other hand, spectrometers with single point or linear array detection systems require simpler mirror systems. Spectrometers using area-array detectors need more complex mirror systems to provide good resolution. It is conceivable that a collimator could be made that would prevent all aberrations; however, this design is expensive because it requires the use of ashperical mirrors.
Smaller two-mirror systems can correct aberrations, but they are not suited for imaging spectrometers. Three mirror systems are compact and correct aberrations as well, but they require at least two asperical components. Systems with more than four mirrors tend to be large and a lot more complex. Catadioptric systems are used in Imagine Spectrometers and are compact, too; however, the collimator or imager will be made up of two curved mirrors and three refracting elements, and thus, the system is very complex.
Optical complexity is unfavorable, however, because effects scatter all optical surfaces and stray reflections. Scattered radiation can interfere with the detector by entering into it and causing errors in recorded spectra. Stray radiation is referred to as “stray light.” By limiting the total number of surfaces that can contribute to scatter, it limits the introduction of stray light into the equation.
Imaging spectrometers are meant to produce well resolved images. In order for this to occur, imaging spectrometers need to be made with few optical surfaces and have no aspherical optical surfaces.
Spectrometers intended for very wide spectral ranges are best if made with all-mirror systems. These particular systems have no chromatic aberrations, and that is why they are preferable. On the other hand, spectrometers with single point or linear array detection systems require simpler mirror systems. Spectrometers using area-array detectors need more complex mirror systems to provide good resolution. It is conceivable that a collimator could be made that would prevent all aberrations; however, this design is expensive because it requires the use of aspherical mirrors.
Smaller two-mirror systems can correct aberrations, but they are not suited for imaging spectrometers. Three mirror systems are compact and correct aberrations as well, but they require at least two asperical components. Systems with more than four mirrors tend to be large and a lot more complex. Catadioptric systems are used in Imagine Spectrometers and are compact, too; however, the collimator or imager will be made up of two curved mirrors and three refracting elements, and thus, the system is very complex.
Optical complexity is unfavorable, however, because effects scatter all optical surfaces and stray reflections. Scattered radiation can interfere with the detector by entering into it and causing errors in recorded spectra. Stray radiation is referred to as “stray light.” By limiting the total number of surfaces that can contribute to scatter, it limits the introduction of stray light into the equation.
Imaging spectrometers are meant to produce well resolved images. In order for this to occur, imaging spectrometers need to be made with few optical surfaces and have no aspherical optical surfaces.
Read more about this topic: Imaging Spectrometer
Famous quotes containing the word systems:
“I am beginning to suspect all elaborate and special systems of education. They seem to me to be built up on the supposition that every child is a kind of idiot who must be taught to think.”
—Anne Sullivan (1866–1936)
“Not out of those, on whom systems of education have exhausted their culture, comes the helpful giant to destroy the old or to build the new, but out of unhandselled savage nature, out of terrible Druids and Berserkirs, come at last Alfred and Shakespeare.”
—Ralph Waldo Emerson (1803–1882)
“The geometry of landscape and situation seems to create its own systems of time, the sense of a dynamic element which is cinematising the events of the canvas, translating a posture or ceremony into dynamic terms. The greatest movie of the 20th century is the Mona Lisa, just as the greatest novel is Gray’s Anatomy.”
—J.G. (James Graham)