Optical Glass On The Elimination Of Chromatic Aberration
Optical glass on the elimination of chromatic aberration
Achromatic: It is conceivable that if a material with a wavelength change the refractive index of the value can be arbitrarily controlled, Optical glass then we can design a completely no color of the lens. Unfortunately, the dispersion of the material can not be controlled arbitrarily. We can imagine that if the visible wavelength band can be divided into blue - green, green - red two intervals, and these two sections can be applied to achromatic technology, the secondary spectrum can be basically eliminated.
However, after calculation: If the green and red achromatic, then the blue color will become very large; if the blue and green achromatic, Optical glass then the red color will become very large. The theoretical calculation for the achromatic find a way, if the manufacture of convex lens low refractive index material blue light on the green part of the relative color difference with the manufacture of concave lens high refractive index of the material relative to the same color difference, then the realization of blue and red achromatic After the green color difference is just eliminated.
This theory points out that the correct way to achieve the achromatic is to find a special optical material whose blue light should be very low relative to the red light and that the partial dispersion of the blue light to the green light should be high and High dispersion material is the same. Fluorite is such a special material, Optical glass its dispersion is very low (Abbe number up to 95.3), and part of the relative dispersion with many optical glass close. The refractive index of fluorite (ie, calcium fluoride, molecular formula CaF2) is relatively low (ND = 1.4339), slightly soluble in water (0.0016g / 100g water), poor machinability and chemical stability, but because of its excellent achromatic Performance makes it a precious optical material. Fluorite was first used only in the microscope, Optical glass since the fluorite artificial crystallization process to achieve after the high super telephoto lens fluorite is almost indispensable material.