Definition
A biological microscope is an instrument that uses the principle of optical magnification to make microscopic observations of transparent or translucent biological samples. It magnifies the fine structure of the sample to the range that the human eye can distinguish through the combination of objective lens and eyepiece, and is widely used in biology, agricultural science, materials inspection and food science, and is one of the basic observation tools in the laboratory.
Principle
Biological microscopes work on the principle of geometric optical imaging. The light from the light source passes through the condenser and hits the sample evenly. The absorption, refraction or diffraction of light by the sample forms a light signal carrying structural information, which is magnified by the objective lens for the first time to form an inverted real image. The real image is further enlarged into a virtual image by the eyepiece twice, and finally received by the human eye. The total magnification is the product of the objective magnification and the eyepiece magnification. The resolution depends on the numerical aperture of the objective lens and the illumination wavelength, and the relationship can be expressed as:d = λ / (2NA)where d is the minimum resolving distance, λ is the wavelength of light, and NA is the numerical aperture of the objective.
Measurement method
When using biological microscopy for observation, standardized procedures are followed. Start by adjusting the Kohler lighting to ensure uniform field of view. The prepared sample slides are then placed on the stage and focused using coarse adjustment and fine-tuning knobs. When observing, it usually starts with a low-power objective, locates the target area, and then switches to a high-power lens to observe details. If microscopic measurement is required, it can be calibrated with the eyepiece micrometer and objective micrometer, and the actual size can be calculated by comparing the image of the sample with the ruler.
Influencing factors
The imaging quality of a microscope is constrained by a variety of factors. The effects of the optical part include the numerical aperture of the objective lens, the level of chromatic and spherical aberration correction, and the degree of matching of the condenser. Lighting conditions such as light source intensity, color temperature, and uniformity can also affect the observation effect. The quality of sample preparation, such as slice thickness, staining contrast, and sealing, directly determines the richness of the observational information. In addition, vibration in the operating environment, stray light in the environment, and the daily maintenance status of the instrument may affect the stability of the observation results.
Application:
In life science research, biological microscopy is used to observe cell morphology, tissue sections, and microbial activity. In the agricultural field, it is used for seed inspection, pest and disease identification. In the food industry, it can be used to monitor microbial contamination of raw materials and the crystal structure of food. In materials science, it is used to observe the microscopic morphology of fibers, paper, or polymer materials. Its observation methods have also expanded from simple brightfield observation to phase contrast, differential interference phase contrast and other contrast-enhancing technologies to meet the observation needs of different samples.
Selection
When choosing a biological microscope, it is necessary to consider the research objectives and operational needs. The core parameters include the magnification range of the objective, the numerical aperture, and the type of aberration correction. The lighting system should consider its brightness adjustable range and lifespan. The mechanical system needs to pay attention to the movement accuracy of the stage and the stability of the focusing mechanism. For scenes that require long-term observation or shared by multiple people, ergonomic design and visual comfort are worth paying attention to. If image recording or analysis is required, the compatibility of the microscope with the camera system needs to be evaluated. Instrument reliability, ease of maintenance, and availability of technical support are also important considerations when meeting functional requirements.