A Compound Microscope is one that uses two or more double convex lenses in focusing the light from the subject to the eyepiece.
The upper lens is typically mounted in the eyepiece, whilst the lower lens lies in the objective. A hollow cylinder is mounted on an adjustable rack allowing the user to make precise adjustments which either raise or lower the device until a clear image of the subject is formed.
A real inverted image is formed by the lower lens when an object is in focus. This inverted image is formed within the main focus of the upper lens. The inverted image now acts as a subject for the upper lens to focus on, the upper lens then producing an image that is further magnified and visible through the eyepiece.
Stereo Microscopes are lower powered microscopes that typically have a larger stage to allow more detailed inspection of non-microscopic subjects. The stereo microscope is also known as a dissecting microscope, and provides a lower level of magnification.
Stereo microscopes are simple and efficient to use, and often used to quickly inspect the quality of diamonds and other gemstones. The magnification makes any internal flaws and surface imperfections immediately apparent.
Inexpensive stereo microscopes are available for children, however the quality of the optics is generally very poor. A professional stereo microscope typically has much higher quality optics, a zoom function, greatly enhanced lighting systems and a more robust construction. These are all required to meet the demands of professional laboratory use.
To produce images, electron microscopes use beams of electrons as opposed to visible light. Electron microscopes have incredible resolving power and are able to magnify extremely small detail. This is because the wavelength of an electron beam is around 100,000 times shorter than the wavelength of visible light photons. A visible light microscope can typically resolve up to 2000x magnification whereas an electron microscope will magnify up to around 10,000,000x.
The electron microscope was invented by German physicist Ernst Ruska, and demonstrated in 1931. It wasn’t until four years later that the electron microscope surpassed the resolution of a light microscope.
Since Ruska introduced the electron microscope, his invention has developed into one of the most advanced tools used in the medical world today.
Electron microscopes have a number of disadvantages, the main one being the cost involved in purchasing and maintenance. Where high resolution is required, electron microscopes need to be housed in stable buildings (often underground) with expensive magnetic field cancelling systems.
The most recent advancement in microscopy has been the introduction of the digital microscope. The digital microscope is simply one which employs the use of a digital camera in imaging. Digital microscopes utilize USB technology to feed live images of the subject that can be viewed on a large monitor.
Digital microscopes typically employ an inverted lens design, enabling specimens of various shapes and sizes to be easily viewed with very little preparation. An adjustable lamp allows the illumination of opaque samples by reflected light.
Similar to digital microscopes, video microscopes use digital imaging technology to offer a range of features that enhance user experience.
The digital cameras within a video microscope system offer high resolution imaging and high sensitivity and are suitable in a wide range of applications. Video microscopes excel at offering low-light level fluorescence imaging efficiently.
Scanning Tunnelling Microscopes
Scanning probe microscopy employs the use of Scanning Tunnelling Microscopes. These microscopes are able to resolve small images of conductive surfaces, and can be used to inspect areas as small as 0.2 nanometres.
A Scanning Tunnelling Microscope can manipulate the atoms of the material being inspected using its tip. The tip of the microscope is connected to a positioning device, computer and scanner and transmits information.
A scanning tunnelling microscope allows the user to understand the position of individual atoms, by visualising areas of high electron density.
Confocal microscopy is used to attain high-resolution images which are restructured to create a three dimensional picture of the scanned subject. Confocal Microscopy provides high-resolution detailed clear images of the object which can give the scientist an in-depth picture. Confocal microscopy employs the use of a computer in processing to enhance image production. Modern examples typically employ lasers for greatly enhanced accuracy.