According to the generation principle of crystal cone light diagram, the incident light must be convergent polarized light. However, the light emitted by the laser is basically collimated linearly polarized light through the polarizer. Therefore, it is necessary to add a piece of glass to change the collimated linearly polarized light into diffusely scattered linearly polarized light radiating in all directions, and its convergent part interferes in the crystal to form a crystal cone light pattern. A dark cross pattern runs through the whole pattern, surrounded by concentric interference rings with alternating light and dark. The center of the cross is also the center of the ring, corresponding to the optical axis direction of the crystal, and the cross direction corresponds to the deflection axis direction of the two deflection plates. Fine-tune the crystal repeatedly in the observation process, so that the center of the interference pattern is coordinated with the photoelectric position, and the pattern is as symmetrical and complete as possible to ensure the light.
The light beam is parallel to the optical axis of the crystal and passes through the center of the crystal. Adjust the polarizer to make the interference pattern appear clear dark cross, one of which is parallel to the X axis.
When a conical light interference pattern appears, the symmetry of the pattern can be used to adjust the optical path. If the light path is collimated, then the cone light interferogram should show good symmetry, otherwise the optical instrument will not be completely collimated and needs constant adjustment.