Definition
A trinocular biological inverted microscope is an optical instrument designed for observing biological samples such as living cells and tissues in culture vessels (such as petri dishes and flasks). Its core feature is that the optical path system is located below the sample, the objective lens is imaged from below upwards, and it is equipped with three eyepiece ports, two of which are used for binocular observation, and the third is usually used to connect image acquisition equipment (such as digital cameras), so that observation and recording can be carried out synchronously. This instrument is a fundamental tool for conducting non-invasive dynamic research in cell biology, microbiology, and more.
Principle
The working principle of a trinocular biological inverted microscope is based on geometric optical imaging. The light source is typically located at the top of the microscope, and the light penetrates the bottom of the culture vessel from top to bottom, shining onto the sample inside the vessel. The transmitted light carrying the sample information is collected and converged by the objective lens below to form a primary magnified real image. The real image passes through the internal prism splitting system, and part of the light is directed to the binocular observation light path for the user to observe through the eyepiece. The other part of the light is directed to the third eyepiece port and projected onto the target surface of the image sensor, which is converted into a digital image signal. Its basic magnification follows the formula: total magnification = objective magnification × eyepiece magnification. If a camera system is connected, the final display magnification also takes into account factors such as display size and sensor size.
Measurement and observation methods
Observation and measurement using a trinocular biological inverted microscope requires a systematic operating procedure. Start by adjusting the Kohler lighting to ensure uniform field of view. The culture vessel containing the sample is then placed on the stage and visualized with a coarse fine focus knob. For dynamic observation of live cells, it is necessary to maintain a stable culture environment and enhance the contrast of unstained samples using special optical techniques such as phase contrast or differential interference contrast. Quantitative measurements, such as cell size or quantity statistics, are typically done in conjunction with eyepiece micrometers or through image analysis software connected to the third port. The software can be based on pixel calibration to achieve semi-automated measurement of parameters such as length, area, and count.
Influencing factors
Imaging quality and measurement accuracy are affected by multiple factors. In terms of optical factors, the numerical aperture of the objective lens determines the resolution and light-gathering ability, while the level of aberration correction affects the image fidelity. Among environmental factors, mechanical vibration can cause blurred images, and ambient stray light can reduce contrast. The sample's own factors, such as the thickness, uniformity, and optical material at the bottom of the culture vessel, can directly affect light transmission and introduce optical distortion. In addition, operational factors such as accurate lighting adjustment, precise focusing, and image sensor performance all have a direct impact on the final result.
Applications
The instrument is widely used in many life sciences and related industries. In basic research, it is used for cell culture status monitoring, cell proliferation and apoptosis research, embryo manipulation, etc. In the field of biotechnology, it is used in cell fusion, transgenic cell screening and other processes. In the industrial sector, such as food microbiological testing, water quality microbiological analysis, and quality monitoring during the production of biological products. Its non-destructive, real-time, and recordable characteristics make it a tool for the study of dynamic biological processes.
Selection considerations
Selection should be comprehensively evaluated based on specific application requirements. The optical system is the core, and it is necessary to pay attention to the numerical aperture, working distance, and support for observation techniques such as phase contrast and fluorescence. Mechanical systems should look at the stage's range, accuracy, and stability, as well as its adaptability to multiple culture vessel specifications. The interface standard for the third port must be compatible with existing or planned image acquisition equipment. In addition, ergonomics, reliability for long-term use and the possibility of subsequent functional expansion are also important considerations. It is recommended to comprehensively evaluate the imaging effect and ease of operation through actual sample testing.