Wherein, according to frequency of the grating strain rosette on three directions and used laser wavelength, calculating opposite angles; splitting beam from laser into six-beam three-couple coherent light past a beam-expand mirror, a alignment mirror and six reflection mirrors; arranging a reflecting mirror on every light path equally to focus six beams on platform center; selecting beam-expand mirror, a space filter and an alignment mirror to obtain even plane wave front; determining the optimal exposure time for holographic grating; arranging light paths according to former angles, setting the holographic dry plate on platform; exposing, developing, fixing, and obtaining the target. This invention is simple but can obtain diffraction strength on different directions. |