Adjustment method and adjustment apparatus for mutual parallelism of two back-to-back gratings

An adjustment method for mutual parallelism of two back-to-back gratings, comprising parallelism adjustment of grating surfaces of the two back-to-back gratings and parallelism adjustment of grating lines of the two back-to-back gratings, and comprising the following steps:

• S11) fixedly disposing a collimating light source that can emit horizontal collimating light backward on the surface of a workbench, and disposing a pinhole diaphragm behind the collimated light source;
• S12) placing a rotation control table on the surface of the workbench behind the pinhole diaphragm, with a lower end of a grating mounting plate being fixedly mounted to the rotation control table and rotatable around a vertical axis;
• fixedly fitting a first grating A and a second grating B back to back to both sides of the grating mounting plate, with the first grating A and/or second grating B being rotatable around an axis perpendicular to both sides of the grating mounting plate;
• S13) rotating the grating mounting plate so that the first grating A faces the pinhole diaphragm and horizontal collimated light emitted by the collimated light source backward passes through the pinhole diaphragm to be incident on the first grating A, and adjusting a deflection angle or pitch angle of the first grating A so that reflected light returns via the pinhole diaphragm, that is, the first grating A is perpendicular to the horizontal collimated light;
• then rotating the grating mounting plate so that the second grating B faces the pinhole diaphragm and horizontal collimated light emitted by the collimated light source backward passes through the pinhole diaphragm to be incident on the second grating B, and adjusting a deflection angle or pitch angle of the second grating B so that reflected light returns via the pinhole diaphragm, that is, the second grating B is perpendicular to the horizontal collimated light, thereby achieving parallelism adjustment of the grating surfaces of the two gratings;
• S14) fixedly disposing a red light source and a receiving screen on an upper side of the surface of the workbench behind the rotation control table, wherein the red light source emits forward infrared light;
• S15) rotating the grating mounting plate so that the first grating A faces the red light source and is perpendicular to the infrared light, wherein a diffraction pattern is displayed on the receiving screen by marking two or more diffraction light spots and connecting marks into a line as the diffraction pattern of the first grating A;
• rotating the grating mounting plate so that the second grating B faces the red light source and is perpendicular to the infrared light, wherein a diffraction pattern is displayed on the receiving screen by marking two or more diffraction light spots and connecting marks into a line as the diffraction pattern of the second grating B;
• S16) if the diffraction pattern of the first grating A is not parallel to the diffraction pattern of the second grating B, proceeding to step S17);
• if the diffraction pattern of the first grating A is parallel to the diffraction pattern of the second grating B, skipping to step S18);
• S17) rotating the first grating A or the second grating B, and returning to step S15);
• and
• S18) completing the parallelism adjustment of the grating lines of the two gratings.