| 摘要 |
PURPOSE:To reduce the crosstalk by arranging two diffraction gratings so that their diffraction directions are vertical to each other and diffusing circularly the power of scattering due to the grating unevenness of the first and the second diffraction gratings. CONSTITUTION:Two transmission type diffraction gratings 1 and 2 are arranged at a proper interval so that their diffraction directions are orthogonal to each other. If two rays of light A and B different in wavelength are allowed to pass them, the rays A and B are separated from each other by an angle thetain one direction by the first diffraction grating 1 and are separated from each other by the angle theta in the direction orthogonal to said direction by the second diffraction grating 2. That is, an incident light 3 is separated on the same line, and the rays A and B are separated in directions orthogonal to each other, and consequently, the reception interval between the rays A and B is about 2<1/2>theta. Thus, the power per unit area is reduced to reduce the crosstalk between the rays A and B. |
