Imaging Principle of Optical Microscope

- May 22, 2019-

Microscope is one of the important tools to study microbiology. According to different research purposes and requirements, ordinary optical microscopy, dark field microscopy, phase contrast microscopy, fluorescence microscopy and electron microscopy can be selected. In food microbiology detection, ordinary optical microscopy (referred to as microscope) is the most commonly used.

Optical microscopy is an optical instrument that uses optical principle to magnify and image small objects that can not be distinguished by human eyes, so as to extract micro-structure information for people. Optical microscopy is the principle of magnifying and imaging an object by means of an optical lens with a curved surface, which enlarges the size of a small object to the human eye.

Optical microscopes are usually magnified by two stages, one by objective and the other by objective. The observed object is located in front of the objective lens, magnified by the objective lens in the first stage, and then the inverted image is magnified by the eyepiece in the second stage. What the human eye sees is a virtual image, and the total magnification of the microscope is the product of the magnification of the objective lens and the magnification of the eyepiece.

Amplification ratio refers to the magnification ratio of the line size, not the area ratio. The limit of the magnification of a microscope is the effective magnification. The resolution of a microscope is the minimum distance between two points that can be clearly distinguished by a microscope. Resolution and magnification are two different but interrelated concepts.

When the resolution of the selected objective is not high enough (the numerical aperture is not large enough), the microscopy can not distinguish the fine structure of the object. At this time, even if the magnification is excessively increased, only a large contour image with unclear details is obtained, which is called invalid magnification. On the other hand, if the resolution has met the requirements and the magnification is insufficient, the microscope has the resolution ability, but because the image is too small, it can not be seen clearly by the human eye. Therefore, in order to give full play to the resolution of the microscope, the numerical aperture and the total magnification of the microscope should be matched reasonably. The structure of the microscope.