Zacharias Jansen and The First Compound Microscope

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Compound Microscopes have assisted scientists in the research of objects invisible to the naked eye for more than four hundred years and have greatly influenced our understanding of the world around us. As technology has progressed, Light Microscopy has significantly improved. These improvements include illumination methods, the Resolution lens quality and the use of oil immersion.
The first compound microscope was invented by Zacharias Jansen and his father Hans in 1595. Whilst experimenting with lenses in a tube Zacharias and his father made an important discovery, where the image of and object at the end of the tube seemed greatly enlarged (history-of-the-microscope.org). This microscope was made of two lenses positioned at each end of a compactable tube. As the tube extended the distance between the lenses grew and the image of an object was enlarged. Unlike the modern compound microscope, there were no illumination methods or use of oil immersion and the quality of the lenses were extremely poor.

Illumination
In comparison to the first compound microscope, modern compound microscopes use various illumination methods to produce high-quality images . Objects are capable of being smaller than a wavelength of light and therefore will not be visible through the microscope. However, wavelengths of light in microscopes can be changed so that light can pass through an object and be magnified. Incandescent tungsten filament bulbs are generally used in microscopes and emit wavelengths of light. Longer wavelengths are towards the infrared end of the spectrum and the shorter wavelengths are towards the ultraviolet end of the spectrum.

Spherical aberration is the blurred image of an object due to parallel light rays passing through t...

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...e slide and the highest power objective lens is brought down until a "bridge" is created between the objective lens and cover slip. Immersion oil possesses a refractive index close to the refractive index of glass; allowing very little refraction of light rays. Resolution quality can be dramatically improved by the use of immersion oil as it increases the numerical aperture of the objective lens (microscope-microscope.org). Oil immersion eliminates chromatic defects and assists in stopping spherical aberration by producing a partially converged light cone before entering the objective lens. With an object at the aplanatic point ( the focal point and in the centre of the field) of the objective lens, there is no spherical aberration. Oil immersion greatly improves resolution, corrects chromatic defects and stops spherical aberration (microscope-microscope.org).

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