| 摘要 |
PURPOSE:To constitute the titled diffraction grating so that a phase variation of a wave surface of diffracted light is varied equally in the repeating direction of a stripe part and in the direction orthogonal to said direction, and also a variation of brightness of the diffracted light in the orthogonal direction concerned is varied to a prescribed shape, by varying a ratio of width of the stripe part in the repeating direction of the stripe part and in the direction orthogonal to said direction. CONSTITUTION:A phase and an intensity of an emitted light L based on an interference of diffracted light beams L1, L2 are varied by a phase difference and a ratio of the intensity of the light beam L1 and L2, and by forming the grating so that a ratio of widths W1, W2 of respective stripe parts 21, 22 is varied by a prescribed value, the emitted light L having a prescribed intensity distribution can be obtained. In this way, by making a variation of a ratio of widths W1, W2 in the repeating direction Y of respective stripe parts 21, 22, equal to a variation of a ratio of the widths W1, W2 in the direction X orthogonal to said direction, the emitted light L having an equal wave surface against the repeating direction Y and the direction X orthogonal to said direction can be obtained, and the emitted light L having no astigmatism can be obtained without being influenced by thickness t1 of the stripe parts 21, 22. |
