Definition
A laboratory optical microscope is an optical instrument that uses visible light and lens systems to magnify the details of tiny objects. It uses the principle of optical magnification to enable observers to distinguish sample structures that cannot be directly seen by the naked eye, and is widely used in materials science, life science research, industrial quality inspection, environmental monitoring and other fields.
Principle
The basic principles of optical microscopy are based on geometric optics and wave optics. Light is emitted from a light source and focused on the sample through a condenser, which absorbs, reflects, or transmits light. The objective lens collects light from the sample and forms a primary magnified reality image, which is then further magnified into a virtual image by the eyepiece for the human eye to see. Magnification is usually the product of the objective lens and the eyepiece magnification. The resolution depends on the numerical aperture and illumination wavelength of the objective lens and can be expressed by the formula: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 measuring with an optical microscope, it usually includes sample preparation, focusing, observation, and recording. Samples need to be sliced, stained or polished to enhance contrast. When measuring dimensions, quantitative analysis can be achieved by calibrating the microscopic scale with the help of eyepiece reticles or digital image analysis software. For transparent samples, transmitted illumination is mostly used; Opaque samples are often epi-illuminated. Some methods involve special optical techniques such as phase contrast, fluorescence, or polarization to obtain specific information.
Influencing factors
The imaging quality of a microscope is influenced by several factors. The numerical aperture and correction level of the objective lens determine the resolution and aberration control. The uniformity and intensity of the lighting system affect the contrast and signal-to-noise ratio. The quality of sample preparation, such as thickness, flatness, and staining uniformity, is directly related to the observation effect. Ambient vibration, temperature fluctuations and cleanliness may also interfere with observation stability. In addition, operator proficiency plays an important role in focusing, optical path adjustment, and instrument maintenance.
Application:
In the industrial sector, optical microscopes are used for metallographic analysis of metal materials, semiconductor defect detection, textile fiber observation, and coating thickness measurement. In scientific research, it supports the study of biological tissue morphology, plant cell structure analysis, and microbial morphology observation. In terms of environmental monitoring, it can be used for particulate counting in water and morphology analysis of air particulate matter. Educational institutions use it as a basic teaching tool to help students understand the microcosm.
Selection
When choosing an optical microscope, it is necessary to consider the observation needs comprehensively. The type of microscope is determined according to the characteristics of the sample, such as stereo microscope is suitable for solid samples, and compound microscope is suitable for thin layer sectioning. The objective lens configuration should consider the magnification range, numerical aperture and working distance. The lighting method needs to match the light transmittance of the sample, and LED light sources are widely used due to their long life and low heat generation. If digital recording is required, attention should be paid to the camera interface and software compatibility. Extended functions such as phase contrast, polarization, or fluorescence modules can be added to meet specific inspection needs. In addition, the mechanical stability, user-friendliness of operation and after-sales service support of the instrument are also reference factors for selection.