Comparison Between Confocal Microscopes and Ordinary Optical Microscopes
A regular biological microscope consists of three parts, namely: ① illumination system, including light source and condenser; ② The optical magnification system, consisting of an objective lens and an eyepiece, is the main body of a microscope. In order to eliminate spherical aberration and chromatic aberration, both the eyepiece and the objective lens are composed of complex lens groups; ③ Mechanical device used for fixing materials and facilitating observation.
The clarity of microscope images is not only determined by the magnification factor, but also by the resolution of the microscope. Resolution refers to the ability of the microscope (or the human eye at a distance of 25cm from the target) to distinguish the smallest distance between objects. The magnitude of resolution depends on the wavelength of light, aperture index, and refractive index of the medium. It can be expressed as:
R=0.61λ /N．A． N．A．＝ｎsinα/2
In the formula: n=refractive index of the medium; α=aperture angle (the angle at which the specimen opens the objective lens aperture), N.A.=numerical aperture. Is the angle of the mirror always less than 180? Therefore, the maximum value of Sina/2 must be less than 1.
The refractive index of glass used to make optical lenses is 1.65-1.78, and the closer the refractive index of the medium used is to glass, the better. For dry objective lenses, the medium is air, and the aperture ratio is generally 0.05~0.95; The oil lens uses cedarwood oil as the medium, and the aperture ratio can be close to 1.5.
The wavelength of ordinary light is 400~700nm, so the resolution value of a microscope will not be less than 0.2 μ m. The resolution of the human eye is 0.2mm, so the maximum magnification factor for microscope design is usually 1000X.
