The application of optical film in microscope

A microscope is an optical system used to observe the extremely fine matter. In addition to fully illuminating the extremely fine matter, its imaging optical system must possibly improve the luminous flux to reduce the loss of light energy reflection. Due to the complexity of the optical system of the microscope, there are as many as 20 optical surfaces. If the antireflection measures are not taken, the light flux may be reduced to 30%. At the same time, the strong reflected light will increase the stray light, which will affect the contrast of the image and damage the quality of the image. Therefore, the antireflection film on the surface of the lens is necessary.

The optical surface of our common microscope objective and eyepiece is blue or purplish red. When the white light passes through the convex lens, the light with shorter wavelength (blue) has a refractivity greater than that of the light with longer wavelength (purplish red). Therefore, when imaging, there are all kinds of spectral circles around the image, and there is a circle of blue or purple red glow. This is to let the yellow green light with wavelength of λ = 550nm pass through, so as to plating magnesium fluoride on the lens. The optical thickness of the film is λ / 4. According to the selective curve of the transmission to the spectrum, the reflection is relatively increased in the red area and the purple area, so the film seen is purplish red or blue.