| 摘要 |
PURPOSE:To prevent a brittle diffraction grating from being exposed so that handling works and maintenance works, such as cleaning, can be performed easily on a double diffraction grating by fixing two grating substrates respectively equipped with diffraction gratings on each one surface of the substrates with their peripheries in a state where the diffractive gratings face each other at an interval. CONSTITUTION:Glass substrates 43 and 44 respectively equipped with photoresist layers 43 and 44 for forming diffraction gratings and diffraction gratings 41 and 42 on each one surface are prepared as the two grating substrates of this double diffraction grating. Such glass substrates 43 and 44 are fixed to each other with an adhesive, etc., by setting the surfaces provided with the diffraction gratings 41 and 42 inward and interposing 47 along the periphery of the substrates 43 and 44. Namely, both diffraction gratings 41 and 42 are faced to each other with an interval and shielded from the outside air by means of the spacers 47. Therefore, a double diffraction grating for which the brittle diffraction gratings are not exposed outside and which can be maintained easily, can be obtained. |
