Reasonable matching of objective lenses and eyepieces of optical microscopes
When selecting objectives and eyepieces, there are two main issues to consider:
First, category matching. That is, all flat-field objectives must be used with special flat-field eyepieces.
Second, reasonable matching of magnification. Under a certain magnification, the objective lens and eyepiece can be combined arbitrarily, but the premise of their combination is mainly to consider the effective magnification, which is an important rule for the correct use of microscopes. The effective magnification of a microscope is 500 to 1000 times the numerical aperture of the objective lens used, that is, the product of the magnification of the objective lens and the eyepiece is equal to 500 to 1000 times the numerical aperture of the objective lens.
If you use a 40X objective lens with a numerical aperture of 0.65 to observe specimens, what size should you choose?
First, calculate the effective total magnification based on the effective magnification, and then divide it by 40 to determine the magnification of the eyepiece that should be selected. The calculation process is: (0.65×500～0.65×1000)÷40≈8～16. In other words: an objective lens with a numerical aperture of 0.65 should be matched with an eyepiece of 8x to 16x within the effective magnification range (500x to 1000x). If the eyepiece power is too low and the total magnification is too small, the resolution of the objective lens cannot be fully exerted, and the details that could have been discerned will be crowded together and difficult to distinguish because the total magnification is too small. The magnification obtained by eyepieces higher than 16 times is called "empty magnification", which does not improve the resolution of details. On the contrary, the depth of clarity is small and cannot clearly reflect different images.
There are many classification methods for optical microscopes
According to the number of eyepieces used, it can be divided into binocular and monocular microscopes; according to whether the image has a three-dimensional sense, it can be divided into stereoscopic vision and non-stereoscopic vision microscopes; according to the observation object, it can be divided into biological and metallographic microscopes; according to the optical principle, it can be divided into Divided into polarizing, phase contrast and differential interference contrast microscopes; according to the type of light source, it can be divided into ordinary light, fluorescence, ultraviolet light, infrared light and laser microscopes; according to the type of receiver, it can be divided into visual and digital (camera) microscopes wait. Commonly used microscopes include binocular stereo microscopes, metallographic microscopes, polarizing microscopes, fluorescence microscopes, etc.
