Techniques for Optical Microscopy Observation
An optical microscope is an optical instrument that uses light as a light source to magnify and observe tiny structures that are invisible to the naked eye. The first microscope was made by an optician in 1604.
Over the past two decades, scientists have discovered that optical microscopes can be used to detect, track and image objects smaller than half the wavelength of conventional visible light, or a few hundred nanometers.
Because light microscopes have not traditionally been used to study the nanoscale, they often lack a calibrated comparison with a standard to check that the results are correct for accurate information at that scale. Microscopy can precisely and consistently indicate the same location of a single molecule or nanoparticle. At the same time, however, it can be highly inaccurate, and the position of an object identified by a microscope to within a billionth of a meter may actually be within a millionth of a meter because there is no error.
Optical microscopes are common among laboratory instruments and can easily magnify different samples ranging from delicate biological samples to electrical and mechanical devices. Likewise, optical microscopes are becoming more capable and affordable as they combine the scientific version of lights and cameras in your smartphone.
Common Observation Methods of Optical Microscopy
Differential Interference Interference (DIC) Observation Method
principle
The polarized light is decomposed into mutually perpendicular and equal-intensity beams through a special prism, and the beams pass through the object at two very close points (less than the resolution of the microscope), so that there is a slight difference in phase, making the image appear three-dimensional Three-dimensional feeling.
features
It can make the object under inspection produce a three-dimensional stereoscopic effect and the observation effect is more intuitive. No special objective lens is needed, it works better with fluorescence observation, and can adjust the color changes of the background and objects to achieve the desired effect.
dark field observation method
Darkfield is actually darkfield illumination. Its characteristics are different from those of bright field. It does not directly observe the light of illumination, but observes the light reflected or diffracted by the object under inspection. Therefore, the field of view is a dark background, while the object under inspection presents a bright image.
The principle of dark field is based on the Tyndall phenomenon in optics. When the dust is directly passed by strong light, the human eye cannot observe it, which is caused by the diffraction of strong light. If the light is cast obliquely on it, due to the reflection of the light, the particle seems to increase in size and is visible to the human eye. A special accessory required for darkfield observation is a darkfield condenser. Its characteristic is that it does not allow the light beam to pass through the object from bottom to top, but changes the path of the light so that it shoots obliquely towards the object, so that the illuminating light does not directly enter the objective lens, and uses the reflection or diffraction light formed by the surface of the object Bright image. The resolution of dark field observation is much higher than that of bright field observation, reaching 0.02-0.004 μm.
