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Microscopes: Illuminating The Micro And Nano Worlds

Light microscopes, which view objects illuminated by visible light, have been around for centuries. Related are instruments that image nonvisible infrared or ultraviolet radiation, or ones that view fluorescence or Raman effects. All of these use opt

Light microscopes, which view objects illuminated by visible light, have been around for centuries. Related are instruments that image nonvisible infrared or ultraviolet radiation, or ones that view fluorescence or Raman effects. All of these use optics to focus light into a viewing field, detector, or camera lens.

The technology behind visible light microscopes, arguably the oldest true laboratory instruments, has not changed much in fundamental operation in 200 years. Microscopes still consist of a light source, optics, and a stage for holding the specimen.

That does not mean that microscopy and microscopes are not evolving, says Lorne Davies, group manager at Olympus America (Center Valley, PA). He admits that innovation tends to be incremental rather than earthshaking, but each stage of improvement “enhances what users are looking for, which is crisp, high-quality images."

For medical and diagnostic laboratory workers, a special focus of Olympus, the most critical improvement is ergonomics. Microscopists working in a cytology or pathology laboratory sit at their instruments for many hours at a time. Ergonomically friendly microscopes help users maintain comfortable body positions, minimize repetitive stress, and lessen fatigue on shoulders and eyes. Ease of use is another related feature in high demand.

One exciting development in light microscopy has been the widespread adoption of fluorescence techniques. Fluorescence microscopy requires specialized reagents and equipment, including a camera to capture fleeting events. One fluorescence method, fluorescent in situ hybridization (FISH), enables investigators to identify and locate specific DNA sequences on chromosomes.

Another emerging technique is whole slide or “virtual” microscopy. This involves capturing microscope images and making them available on computer screens for later examination by one or more individuals. Virtual methods are useful for collaborative work, particularly in medical diagnostics.

What should potential buyers look for before purchasing a microscope? Mr. Davies puts a vendor’s reputation, service, and support high on the list. “People have close relationships with their microscopes, and that closeness extends to companies selling them.”

This past year, Ravikiran Attota, Ph.D., a research engineer at NIST (Gaithersburg, MD), discovered a software technique that he claims provides the resolution of scanning electron microscopy (SEM) or atomic force microscopy (AFM) through a conventional light microscope. The technique, through-focus scanning optical microscopy (TSOM), uses a software trick, and no additional hardware, to reconstruct images rapidly and at low cost.

In fact, Dr. Attota claims that his method improves on SEM and AFM in that it combines their strengths. SEM excels at lateral resolution, while AFM is best for vertical resolution, he says. TSOM achieves both through a paradoxical approach.

Optical microscopes cannot clearly visualize nanometer-scale features because the wavelength of visible light is larger than the object being imaged. Dr. Attota acquires many of these out-of- focus, or through-focus images anyway, at different focal points. The computer program he wrote combines the images and reassembles them into a TSOM image with spectacular depth capabilities. Where AFM provides depth resolution of only 1 micron, TSOM easily reaches 100 microns and in tests has produced images with 200-micron depth resolution.

Recently Released Microscopes

Versa 3D DualBeam

  • Provides high-resolution, three-dimensional (3D) imaging and analysis on a wide range of sample types
  • Highly configurable platform allows customers to adapt the system’s capabilities to their specific requirements
  • Available with either high vacuum-only or high and low vacuum electron imaging hardware

FEI Company


  • Delivers high throughput nano-analysis for process and quality control of mass produced semiconductor and materials samples
  • Features high resolution imaging in TEM, STEM, and SE modes and ultrasensitive elemental mapping with a large angle Energy Dispersive Spectrometer (EDS)
  • Also includes Electron Energy Loss Spectroscopy (EELS)


Upright Two Photon Microscope

  • Designed for in vivo or intravital imaging in live animals
  • Features a non-descanned detection scheme based on two highly sensitive GaAsP PMTS with equivalent collection efficiency
  • Includes a motorized slider with 3 filter sets for flexibility in choice of dyes
  • Lets users combine up to 6 color channels for two-photon imaging

TILL Photonics

Z850, 3035, and 3032PH Series

  • Z850 Stereo Zoom Binocular and Trinocular Microscopes provide superior performance optics at an affordable price
  • The 3035 Series, designed for clinical and research applications, boasts the AIS infinity optical system, renowned for resolution, contrast, and clarity
  • Modular design of the 3032PH Series allows users to add a fluorescence illuminator with a two-position filter cube slider

Warner Instruments