What are the commonly used observation methods for optical microscopes
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 early microscopes were manufactured by opticians in 1604.
In the past twenty years, scientists have discovered that optical microscopes can be used to detect, track, and image objects, which are smaller than half the wavelength of traditional visible light, or several hundred nanometers.
Due to the fact that optical microscopes have not been traditionally used to study the nanoscale, they often lack calibration comparisons with standards to check whether the results are correct and obtain accurate information at that scale. Microscopes can accurately and consistently indicate the same position of individual molecules or nanoparticles. However, at the same time, it can be highly inaccurate, as the position of the object identified by the microscope within the billionth meter may actually be one millionth of a meter, as there are no errors.
Optical microscopes are common in laboratory instruments and can easily magnify different samples, from delicate biological samples to electrical and mechanical equipment. Similarly, optical microscopes are becoming increasingly capable and cost-effective as they combine the scientific versions of lighting and cameras in smartphones.
Common observation methods for optical microscopes
Differential Interference (DIC) Observation Method
principle
By using a specially designed prism, polarized light is decomposed into beams of equal intensity and perpendicular to each other. The beams pass through the object at very close points (less than the resolution of the microscope), resulting in slight differences in phase, giving the image a three-dimensional feel.
characteristic
It can make the inspected object produce a three-dimensional feeling and observe the effect more intuitively. No special objective lens is required, which is better coordinated with fluorescence observation and can adjust the color changes of the background and objects to achieve ideal results.
Dark field observation method
The dark field of view is actually dark field illumination. Its characteristics are different from the bright field of view, where it does not directly observe the illumination light, but instead observes the reflected or diffracted light of the object being tested. Therefore, the field of view is a dark background, while the inspected object presents a bright image.
The principle of dark field of view is based on the optical Tindall phenomenon, where fine dust cannot be observed by the human eye under direct sunlight, which is caused by diffraction of strong light. If the light is slanted towards it, the particles appear to increase in volume and become visible to the human eye due to the reflection of the light. The special accessory required for dark field observation is a dark field condenser. Its characteristic is not to let the light beam pass through the inspected object from bottom to top, but to change the path of the light beam, making it slant towards the inspected object, so that the illumination light does not directly enter the objective lens, and uses the bright image formed by the reflected or diffracted light on the surface of the inspected object. The resolution of dark field observation is much higher than that of bright field observation, reaching 0.02-0.004 μ M.
