Main Performance Parameters of Microscope

A microscope is a precision measuring instrument that allows students to observe extremely small organisms and study their microbial morphology. The main body of the microscope is composed of optical and mechanical parts, among which the optical part is the most important. The optical part of a microscope mainly consists of an objective lens and an eyepiece. By combining the two, a good observation image is formed.

1. Numerical aperture.

Numerical aperture, also known as aperture ratio, mainly refers to the product of the refractive index of the medium between the object and the lens and the sine value of half the aperture of the lens. It is one of the important parameters of a microscope. It is generally believed that a larger numerical aperture value is better, and there are two main ways to increase it. The first is to continuously increase the aperture angle, and the second is to increase the white refractive index.

2. Resolution.

Resolution is one of the main parameters reflecting the performance of a microscope. Generally speaking, the human eye can observe and resolve objects at a distance of 0.073mm. If it is even smaller, it is not easy to distinguish. The working principle of a microscope is similar to that of the human eye, and its minimum resolution also has numerical values. Resolution is also related to numerical aperture, which is determined by two factors: numerical aperture and illumination source wavelength. A larger numerical aperture and shorter wavelength result in higher resolution.

3. Magnification ratio.

The magnification of the objective and eyepiece of a microscope is represented by numbers and letters on the body, and the overall magnification of the microscope refers to the product of the two. When using a microscope, the objective lens is used in conjunction with the eyepiece. When using the eyepiece, attention should be paid to the coordination between the compensating eyepiece and the objective lens. The compensating eyepiece is also marked with certain letters and needs to be used in conjunction with the symbol achromatic objective lens.

4. Working distance.

The working distance mainly refers to the distance between the lower surface of the objective lens and the upper surface of the cover glass after focusing the microscope. The larger the magnification of the objective lens, the shorter the working distance. By way of explanation, the working distance of a low-power objective lens with a magnification of less than 10 times will be around 6mm, while the working distance of a hundredfold objective lens is only less than 0.2mm. One student, while conducting experiments, constantly used a high-power objective lens, and when the focusing was inaccurate, the problem of crushing the slice occurred. With the continuous maturity of the microscope mechanism, this problem is expected to be fundamentally solved. In addition to the main parameters mentioned above, the performance parameters of a microscope include depth of field, poor coverage, field of view, mirror brightness, clarity, etc. These direct or indirect parameters are all related to the observation effect of the microscope.