How do I calibrate the polariser of a polarisation microscope?
In operation, the vibration directions of the upper and lower polarising lenses of the polarising microscope should be orthogonal to each other, or in the east-west and north-south directions, each in line with the cross filament of the eyepiece in the horizontal and vertical directions. Sometimes only one lower polarizer is used for observation, the vibration direction of the lower polarizer must be determined, so the polarizer must be corrected during operation.
1, eyepiece cross filament detection
Generally check whether the eyepiece cross filament is orthogonal, and whether it is consistent with the vibration direction of the upper and lower polarizers, and at the same time, select a piece of black mica with a complete resolution pole, move it to the centre of the eyepiece cross filament, place the resolution slit parallel to one of the cross filaments, write down the number of scales of the carrier table, and then rotate the animal table so that the resolution slit is parallel to the other cross filament, and then write down the number of scales of the carrier table, and the difference of the two scales is 90 °, which means that the cross filaments are orthogonal. The difference between the two scales is 90°, indicating that the cross filaments are orthogonal.
2,Determination and correction of the vibration direction of the lower polariser
Generally, black mica is used to check the vibration direction of the lower polarizer, which is because black mica is a widely distributed transparent mineral. First of all, find a piece of solved and clear black mica, move to the centre of the eyepiece cross filament, launch the upper polarizer, rotate the carrier table for a week, observe the change of the black mica colour, because the black mica vibration of the solved direction of light absorption * strong, so that the black mica colour to * deep, the direction of the solved slit is the direction of the vibration of the lower polarizer.
3,Correction of orthogonality of upper and lower polarizers
After the direction of the lower polarizer is corrected, remove the sheet and push it into the upper polarizer to observe whether the field of view is all black or in an extinction state. If it is all black, the vibration directions of the upper and lower polarisers are orthogonal to each other. Otherwise, the upper polariser must be corrected so that the field of view is * dark. The stop screw of the upper polariser must be loosened when turning, and then tightened after correction.
