Polarizing mirror method for correcting polarizing microscope
In actual operation, the vibration directions of the upper and lower polarizers of the polarizing microscope should be orthogonal to each other, or the east-west or north-south directions, which are consistent with the horizontal and vertical directions of the eyepiece crosshairs respectively. Sometimes only one lower polarizer is used to observe, and the vibration direction of the lower polarizer must be determined, so the polarizer must be corrected during operation.
1, eyepiece crosshair detection
Check whether the crosshairs of the eyepiece are orthogonal and consistent with the vibration direction of the upper and lower polarizers. At the same time, select a piece of biotite with complete cleavage, move it to the center of the crosshair of the eyepiece, make the cleavage seam parallel to one of the crosshairs, and record the scale number of the loading table, then turn the animal table to make the cleavage seam parallel to the other crosshair, and record the scale number of the loading table. The difference between the two scales is 90, indicating that the crosshairs are orthogonal.
2. Determination and correction of vibration direction of lower polarizer.
Using biotite to check the vibration direction of the lower polarizer is because biotite is a widely distributed transparent mineral, which is very characteristic under single polarization. First, find a piece of clear biotite with cleavage, move it to the center of the crosshair of the eyepiece, push out the upper polarizer, rotate the stage for one week, and observe the change of biotite color. Because biotite absorbs the vibration light in the cleavage direction strongly, when the biotite color reaches * depth, the direction of cleavage seam is the vibration direction of the lower polarizer.
3. Correction of orthogonality of upper and lower polarizers
After the direction of the lower polarizer is corrected, take off the sheet, push it into the upper polarizer, and observe whether the visual field is completely black or not. If it is all black, it means that the vibration directions of the upper and lower polarized light are orthogonal to each other. Otherwise, the upper polarizer should be corrected, that is, the upper polarizer should be rotated to make the view reach the darkest. When rotating, you must loosen the stop screw of the upper polarizer first, and then tighten it after correction.
